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Peer-reviewed articles

2016

Walther,H., Subbaraman,L., Jones,L. W. In vitro cholesterol deposition on daily disposable contact lens materials. Optometry and Vision Science 2016;93,1:36-41. [ Show Abstract ]

Purpose. The goal of this study was to analyze how various incubation times affect the uptake of cholesterol on silicone hydrogel (SH) and conventional hydrogel (CH) daily disposable (DD) contact lens materials using an in vitro radiochemical detectionmethod. Methods. Three SH (somofilcon A, delefilcon A, and narafilcon A) and four CH (etafilcon A, nesofilcon A, ocufilcon A, and nelfilcon A) contact lenses were incubated in an artificial tear solution that contained major tear film components and a portion of radioactive 14C-cholesterol. Lenses (N = 4) were incubated for four incubation times (2, 6, 12, or 16 h) to assess the effects on cholesterol deposition. Subsequent to the incubation, the lenses were extracted using 2:1 chloroform:methanol, and the extracts were analyzed in a beta counter and (in nanograms per lens) extrapolated from standard curves. Results. In general, cholesterol deposited statistically significantly more on SH lenses than CHs (p e 0.033), with the exception of somofilcon A and nesolfilcon A materials (p = 0.067). Within the SH materials, narafilcon A accumulated the largest quantity of cholesterol (p G 0.05) and somofilcon A the lowest (p G 0.05). The uptake of cholesterol ranged from 22.63 T 2.98 ng/lens to 97.94 T 4.18 ng/lens for all lens materials. The accumulation of cholesterol was shown to be continuous throughout the 16 h of incubation, without reaching a plateau (p G 0.001). Conclusions. For the periods thatDDlens materials are worn, cholesterol deposits significantlymore ontoSHcontact lenses than CHs. This could have implications for wearers who have higher levels of lipid in their tears that are fitted with SH DD materials. Copyright © American Academy of Optometry.

Jones,L. W., Byrne,M., Ciolino,J. B., Legerton,J., Markoulli,M., Papas,E., Subbaraman,L. Revolutionary future uses of contact lenses. Optometry and Vision Science 2016;93,4:325-327.

Phan,C. -M, Walther,H., Gao,H., Rossy,J., Subbaraman,L. N., Jones,L. Development of an in Vitro ocular platform to test contact lenses. Journal of Visualized Experiments 2016;2016,110:e53907. [ Show Abstract ]

Currently, in vitro evaluations of contact lenses (CLs) for drug delivery are typically performed in large volume vials,1-6 which fail to mimic physiological tear volumes.7 The traditional model also lacks the natural tear flow component and the blinking reflex, both of which are defining factors of the ocular environment. The development of a novel model is described in this study, which consists of a unique 2-piece design, eyeball and eyelid piece, capable of mimicking physiological tear volume. The models are created from 3-D printed molds (Polytetrafluoroethylene or Teflon molds), which can be used to generate eye models from various polymers, such as polydimethylsiloxane (PDMS) and agar. Further modifications to the eye pieces, such as the integration of an explanted human or animal cornea or human corneal construct, will permit for more complex in vitro ocular studies. A commercial microfluidic syringe pump is integrated with the platform to emulate physiological tear secretion. Air exposure and mechanical wear are achieved using two mechanical actuators, of which one moves the eyelid piece laterally, and the other moves the eyeballeyepiece circularly. The model has been used to evaluate CLs for drug delivery and deposition of tear components on CLs.

Phan,C. -M, Subbaraman,L., Jones,L. W. The use of contact lenses as biosensors. Optometry and Vision Science 2016;93,4:419-425. [ Show Abstract ]

The tear film is a complex multilayer film consisting of various proteins, enzymes, and lipids and can express a number of biomarkers in cases of disease. The development of a contact lens sensor presents a noninvasive alternative for the detection and management of various diseases. Recent work has resulted in the commercialization of a device to monitor intraocular pressure for up to 24 h, and there are extensive efforts underway to develop a contact lens sensor capable of continuous glucose tear film monitoring to manage diabetes. This clinical perspective will highlight the major developments within this field and list some of the major challenges that still need to be addressed. © 2015 American Academy of Optometry.

Phan,C. -M, Bajgrowicz,M., Gao,H., Subbaraman,L. N., Jones,L. W. Release of fluconazole from contact lenses using a novel in vitro eye model. Optometry and Vision Science 2016;93,4:387-394. [ Show Abstract ]

Purpose. Rapid drug release followed by a plateau phase is a common observation with drug delivery from contact lenses (CLs) when evaluated in a vial. The aim of this study was to compare the release of fluconazole from seven commercially available daily disposable CLs using a conventional vial-based method with a novel in vitro eye model. Methods. An eye model was created using two 3-dimensional printed molds, which were filled with polydimethylsiloxane to obtain an inexpensive model that would mimic the eyeball and eyelid. The model was integrated with a microfluidic syringe pump, and the flow-through was collected in a 12-well microliter plate. Four commercial daily disposable conventional hydrogels (nelfilcon A, omafilcon A, etafilcon A, ocufilcon B) and three silicone hydrogels (somofilcon A, narafilcon A, delefilcon A) were evaluated. These CLs were incubated with fluconazole for 24 h. The drug release was measured in a vial containing 4.8 mL of phosphate-buffered saline and in the polydimethylsiloxane eye model with a 4.8-mL tear flow across 24 h. Results. Overall, conventional hydrogel CLs had a higher uptake and release of fluconazole than silicone hydrogel CLs (p < 0.05). A higher drug release was observed in the vial condition compared with the eye model (p < 0.001). In the vial system, the drugs were rapidly released from the CL within the first 2 h, followed by a plateau phase. In contrast, drug release in the eye model under low tear volume was sustained and did not reach a plateau across 24 h (p < 0.05). Conclusions. Rapid drug release results from using a vial as the release system. Under low tear volume at physiological tear flow, commercial CLs can maintain a sustained drug release profile for up to 24 h. However, eyes with fungal keratitis may have increased tearing, which would significantly accelerate drug release. © 2015 American Academy of Optometry.

Liu,L. Y., Seo,J., McCanna,D. J., Subbaraman,L. N., Jones,L. W. Assessment of biofilm formation of E. meningoseptica, D. acidovorans, and S. maltophilia in lens cases and their growth on recovery media. Contact Lens and Anterior Eye 2016;39,2:117-123. [ Show Abstract ]

Purpose: Bacterial biofilm formation in contact lens cases is a risk factor in the development of both microbial and infiltrative keratitis. This investigation evaluated three emerging pathogens: Stenotrophomonas maltophilia, Elizabethkingia meningoseptica, and Delftia acidovorans for biofilm formation and metabolic activity in lens cases. Also, growth of these bacteria on different media was assessed to optimize recovery conditions. Methods: The three bacteria were incubated in lens cases with different concentrations of tryptic soy broth. Biofilm formation was evaluated by measuring metabolic activity using MTT and enumerating the number of viable bacteria. To determine the optimal recovery media, dilutions of these microorganisms were plated on six different media. The number of colony forming units (CFU) was recorded after 48, 72, and 96 h of incubation at 32 °C and 37 °C for S. maltophilia, and at 37 °C for E. meningoseptica and D. acidovorans. Results: All three microorganisms established biofilms in the lens cases, with significant numbers of CFU recovered. Biofilms of S. maltophilia and E. meningoseptica were metabolically active. Significant reduction in metabolic activity and number of viable S. maltophilia occurred when the incubation temperature was raised from 32 °C to 37 °C (p < 0.05). The metabolic activity of the biofilms increased with greater organic load present. The highest percent recovery for all three organisms was given by Columbia blood agar, followed by chocolate. Conclusion: Based on the results, the presence of the three emerging pathogens present in lens cases and from corneal isolates can be accurately determined if proper growth media and incubation temperatures are utilized.

Dantam,J., McCanna,D. J., Subbaraman,L. N., Papinski,D., Lakkis,C., Mirza,A., Berntsen,D. A., Morgan,P., Nichols,J. J., Jones,L. W., Mathew,J. H., Cox,S. M., Bickle,K. M., Powell,D. R., Cox,J., Miller,W. L., Wallace-Tucker,A., Charrier,S., Chen,Y. -J, Cardenas,L., Huerta,S., Dionne,K., Maldonado-Codina,C., Plowright,A. J., Howarth,G. F., Chatterjee,N., Smith,S., Dumbleton,K., Schulze,M., Moezzi,A., Luensmann,D., Ngo,W., Paquette,L., Srinivasan,S., Varikooty,J., Johnson,J., Simpson,M., Voss,L., R Microbial contamination of contact lens storage cases during daily wear use. Optometry and Vision Science 2016;93,8:925-932. [ Show Abstract ]

Purpose. To evaluate contact lens (CL) storage case contamination when used with four different CL care solutions during daily wear of three different CL materials. Methods. A parallel, prospective, bilateral, randomized clinical trial (n = 38) was conducted. Subjects were randomly assigned to use one of three CL materials (etafilcon A, senofilcon A, or galyfilcon A) on a daily wear basis. Subsequently, each subject randomly used one of four different CL care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and CLEAR CARE) for 2 weeks, along with their respective storage cases. After every 2-week period, their storage cases were collected and the right and left wells of each storage case were randomized for two procedures: (1) microbial enumeration by swabbing the storage case surface and (2) evaluation of biofilm formation (multipurpose solution cases only) using a crystal violet staining assay. Results. More than 80% of storage cases were contaminated when used in conjunction with the four CL care solutions, irrespective of the CL material worn. Storage cases maintained with CLEAR CARE (mean Log colony forming units (CFU)/ well ± SD, 2.0 ± 1.0) revealed significantly (p < 0.001) greater levels of contamination, compared to those maintained with Biotrue (1.3 ± 0.8) and RevitaLens OcuTec (1.2 ± 0.8). Predominantly, storage cases were contaminated with Gram-positive bacteria (= 80%). There were significant differences (p = 0.013) for the levels of Gram-negative bacteria recovered from the storage cases maintained with different CL care solutions. Storage cases maintained withOPTI-FREE PureMoist (0.526 ± 0.629) showed significantly higher biofilm formation (p = 0.028) compared to those maintained with Biotrue (0.263 ± 0.197). Conclusions. Levels of contamination ranged from 0 to 6.4 Log CFU/storage case well, which varied significantly (p < 0.001) between different CL care solutions, and storage case contamination was not modulated by CL materials. © Copyright 2016 American Academy of Optometry.

Omali,N. B., Heynen,M., Subbaraman,L. N., Papinski,D., Lakkis,C., Smith,S. L., Morgan,P. B., Berntsen,D. A., Nichols,J. J., Jones,L. W., Mathew,J. H., Cox,S. M., Bickle,K. M., Powell,D. R., Cox,J., Miller,W. L., Wallace-Tucker,A., Charrier,S., Chen,Y. -J, Cardenas,L., Huerta,S., Dionne,K., Maldonado-Codina,C., Plowright,A. J., Howarth,G. F., Chatterjee,N., Mirza,A., Dumbleton,K., Schulze,M., Moezzi,A. M., Luensmann,D., Ngo,W., Paquette,L., Srinivasan,S., Varikooty,J., Johnson,J., Simpson,M., Vos Impact of lens care solutions on protein deposition on soft contact lenses. Optometry and Vision Science 2016;93,8:963-972. [ Show Abstract ]

Purpose. To evaluate the effect of four contemporary lens care solutions on total protein, total lysozyme, and active lysozyme extracted from three contact lens materials. Methods. Adapted contact lens wearers were recruited at three sites, and all subjects were randomly assigned to daily wear of either etafilcon A, galyfilcon A, or senofilcon A for 2 weeks. Four lens care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and ClearCare) were used by each subject in random order with a new pair of lenses after a washout period between solutions of at least 4 days. After 2 weeks of daily wear, contact lenses were collected for analysis. Proteins were extracted from a subset of contact lenses (n = 568) and total protein, total lysozyme, and lysozyme activity were quantified using a modified Bradford assay, an enzyme-linked immunosorbent assay, and a micrococcal assay, respectively. Results. Higher levels of total protein were extracted from etafilcon A when used with Biotrue compared to other solutions (p = 0.0001). There were higher levels of total lysozyme extracted from galyfilcon A lenses when used with PureMoist than with Biotrue or Clear Care (p < 0.006). Higher total lysozyme was extracted from senofilcon A when used with RevitaLens OcuTec compared to Biotrue (p = 0.002). Lower lysozyme activity was recovered from senofilcon A lenses with RevitaLens OcuTec when compared to all other care solutions (all p < 0.004). When Biotrue, PureMoist, or RevitaLens OcuTec were used, higher total lysozyme was extracted from galyfilcon A compared to senofilcon A(p < 0.01). When RevitaLens OcuTec was used, higher levels of active lysozyme were extracted from galyfilcon A compared to senofilcon A (p = 0.02). Conclusions. The ability of lens care solutions to remove protein from lenses varies depending upon the care solution composition and also the polymeric make-up of the contact lens material. © Copyright 2016 American Academy of Optometry.

Muntz,A., van Doorn,K., Subbaraman,L. N., Jones,L. W. Impression cytology of the lid wiper area. Journal of Visualized Experiments 2016;2016,114:. [ Show Abstract ]

Few reports on the cellular anatomy of the lid wiper (LW) area of the inner eyelid exist and only one report makes use of cytological methods. The optimization of a method of collecting, staining and imaging cells from the LW region using impression cytology (IC) is described in this study. Cells are collected from the inner surface of the upper eyelid of human subjects using hydrophilic polytetrafluoroethylene (PTFE) membranes, and stained with cytological dyes to reveal the presence of goblet cells, mucins, cell nuclei and various degrees of pre- and parakeratinization. Immunocytochemical dyes show cell esterase activity and compromised cell membranes by the use of a confocal scanning laser microscope. Up to 100 microscopic digital images are captured for each sample and stitched into a high-resolution, large scale image of the entire IC span. We demonstrate a higher sensitivity of IC than reported before, appropriate for identifying cellular morphologies and metabolic activity in the LW area. To our knowledge, this is the first time this selection of fluorescent dyes was used to image LW IC membranes. This protocol will be effective in future studies to reveal undocumented details of the LW area, such as assessing cellular particularities of contact lens wearers or patients with dry eye or lid wiper epitheliopathy. © 2016 Journal of Visualized Experiments.

Phan,C. -M, Bajgrowicz,M., McCanna,D. J., Subbaraman,L. N., Jones,L. Effects of Antifungal Soaked Silicone Hydrogel Contact Lenses on Candida albicans in an Agar Eye Model. Eye and Contact Lens 2016;42,5:313-317. [ Show Abstract ]

Purpose: To evaluate the effects of two commercial silicone hydrogel contact lenses (CLs) soaked with natamycin (NA) or fluconazole (FL) on the growth of Candida albicans in an in vitro eye model. Methods: Three-D printed molds were used as a cast for making eye-shaped models comprising potato dextrose agar. Senofilcon A (SA) and lotrafilcon B (LB) CLs were incubated with either 2 mL of NA or FL at a concentration of 1 mg/mL for 24 hr. To simulate a fungal infection, the eye models were coated with C. albicans. The drug-soaked lenses were placed on top of the eye models. Seven experimental conditions were examined: (1) NA-SA, (2) NA-LB, (3) FL-SA, (4) FL-LB, (5) SA, (6) LB, and (7) control - no lens. At specified time points (t1, 8, 16, 24, 48 hr), the agar eyes from each experimental condition were removed from the incubator and photographed. The yeast cells from the 24 and 48 hr time point were also analyzed using light microscopy. Results: At 24 and 48 hr, there was considerable growth observed for all conditions except for the NA-SA and NA-LB conditions. When observed under the microscope at 24 and 48 hr, the morphology of the yeast cells in the FL-SA and SA condition were similar to that of the control (oval shaped). There was limited hyphae growth observed for LB and significant visible hyphae growth for the NA-LB group. For NA-SA, NA-LB, and FL-LB groups, the cells were significantly smaller compared with the control. Conclusions: For NA-SA and NA-LB, there was limited growth of C. albicans observed on the eye models even after 48 hr. Under the microscope, the cell morphology differ noticeably between each testing condition, and is dependent on drug-lens combinations. © 2015 Contact Lens Association of Ophthalmologists.

2015

Muntz,A., Subbaraman,L. N., Sorbara,L., Jones,L. Tear exchange and contact lenses: A review. Journal of Optometry 2015;8,1:2-11. [ Show Abstract ]

Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses.

Chang,J. M. L., McCanna,D. J., Subbaraman,L. N., Jones,L. W. Efficacy of antimicrobials against biofilms of achromobacter and pseudomonas. Optometry and Vision Science 2015;92,4:506-513. [ Show Abstract ]

Purpose. Achromobacter xylosoxidans and Pseudomonas aeruginosa biofilms can develop in ophthalmic products and accessories such as contact lens cases, leading to the development of ocular infections. This study evaluated the efficacy of the antimicrobials polyaminopropyl biguanide (PAPB) and benzalkonium chloride (BAK) against A. xylosoxidans and P. aeruginosa biofilms. Methods. Biofilms of A. xylosoxidans and P. aeruginosa used as a comparative control were formed by incubating the bacteria on contact lens cases and on coverslips in phosphate-buffered saline. The biofilms were then exposed to PAPB and BAK for 5 minutes and 4 hours. After exposure, alginate swabs were used to remove the biofilms from the lens cases and the bacteria were plated on tryptic soy agar for determination of survivors. Also, after exposure to these disinfectants, the A. xylosoxidans and P. aeruginosa biofilms were stained with SYTO 9 and propidium iodide. Using a confocal microscope with a 488-nm laser, the number of cells with damaged cell membranes was determined. Results. After 5 minutes of exposure to BAK or PAPB, A. xylosoxidans biofilms were more resistant to the antimicrobial effects of these disinfectants than P. aeruginosa biofilms. After 4 hours, both organisms were reduced by more than 3 logs after exposure to either BAK or PAPB. Confocal microscopy studies revealed that BAK was more effective at damaging A. xylosoxidans and P. aeruginosa cell membranes than PAPB at the concentrations used in ophthalmic products. Conclusions. Biofilms of the emerging pathogen A. xylosoxidans were more resistant to the disinfectants PAPB and BAK than biofilms of P. aeruginosa. Because of the emergence of A. xylosoxidans and the demonstrated greater resistance to the common ophthalmic preservatives BAK and PAPB than the standard Gram-negative organism P. aeruginosa, A. xylosoxidans biofilms should be assessed in antimicrobial challenge tests to assure the safety of multiuse ophthalmic products. Copyright © 2015 American Academy of Optometry.

Omali,N. B., Subbaraman,L. N., Coles-Brennan,C., Fadli,Z., Jones,L. W. Biological and clinical implications of lysozyme deposition on soft contact lenses. Optometry and Vision Science 2015;92,7:750-757. [ Show Abstract ]

Within a few minutes of wear, contact lenses become rapidly coated with a variety of tear film components, including proteins, lipids, and mucins. Tears have a rich and complex composition, allowing a wide range of interactions and competitive processes, with the first event observed at the interface between a contact lens and tear fluid being protein adsorption. Protein adsorption on hydrogel contact lenses is a complex process involving a variety of factors relating to both the protein in question and the lens material. Among tear proteins, lysozyme is a major protein that has both antibacterial and anti-inflammatory functions. Contact lens materials that have high ionicity and high water content have an increased affinity to accumulate lysozyme during wear, when compared with other soft lens materials, notably silicone hydrogel lenses. This review provides an overview of tear film proteins, with a specific focus on lysozyme, and examines various factors that influence protein deposition on contact lenses. In addition, the impact of lysozyme deposition on various ocular physiological responses and bacterial adhesion to lenses and the interaction of lysozyme with other tear proteins are reviewed. This comprehensive review suggests that deposition of lysozyme on contact lens materials may provide a number of beneficial effects during contact lens wear. © 2015 American Academy of Optometry.

Bajgrowicz,M., Phan,C. -M, Subbaraman,L. N., Jones,L. Release of ciprofloxacin and moxifloxacin from daily disposable contact lenses from an in vitro eye model. Investigative Ophthalmology and Visual Science 2015;56,4:2234-2242. [ Show Abstract ]

Purpose. To analyze the release of two fluoroquinolones, ciprofloxacin and moxifloxacin, from conventional hydrogel (CH) and silicone hydrogel (SH) daily disposable contact lenses (CLs), comparing release from a fixed-volume vial and a novel in vitro eye model. Methods. Four CH CLs (nelfilcon A, omafilcon A, etafilcon A, ocufilcon B) and three SH CLs (somofilcon A, narafilcon A, delefilcon A) were used. The lenses were incubated in drug solutions for 24 hours. After the incubation period, the lenses were placed in two release conditions: (1) a vial containing 4.8 mL PBS for 24 hours and (2) an in vitro eye model with a flow rate at 4.8 mL over 24 hours. Results. Release in the vial for both drugs was rapid, reaching a plateau between 15 minutes and 2 hours for all lenses. In contrast, under physiological flow conditions, a constant and slow release was observed over 24 hours. The amounts of ciprofloxacin released from the lenses ranged between 49.6 ±0.7 and 62.8 ± 0.3 µg per lens in the vial, and between 35.0 ± 7.0 and 109.0 ± 5.0 µg per lens in the eye model. Moxifloxacin release ranged from 24.0 ± 4.0 to 226.0 ± 2.0 µg per lens for the vial, and between 13.0 ± 2.0 and 151.0 ± 10.0 µg per lens in the eye model. In both systems and for both drugs, HEMA-based CLs released more drugs than other materials. Conclusions. The parameters of the release system, in particular the volume and flow rate, have a significant influence on measured release profiles. Under physiological flow, release profiles are significantly slower and constant when compared with release in a vial. © 2015, The Association for Research in Vision and Ophthalmology, Inc.

Samsom,M., Chan,A., Iwabuchi,Y., Subbaraman,L., Jones,L., Schmidt,TA In vitro friction testing of contact lenses and human ocular tissues: Effect of proteoglycan 4 (PRG4). Tribology International 2015;8927-33. [ Show Abstract ]

Contact lens friction was recently shown to correlate with in vivo comfort, with lower friction lenses providing improved comfort. Proteoglycan 4 (PRG4) is a recently discovered ocular surface boundary lubricant. The objectives of this study were to measure the friction of commercially available silicone hydrogel (SiHy) contact lenses against human cornea and eyelid tissues, and evaluate the ability of PRG4 to lubricate, and adhere to, SiHy contact lenses. The in vitro friction test employed here effectively measured and distinguished the SiHy contact lens friction coefficients against human eyelid and cornea tissues, and PRG4 functioned as an effective boundary lubricant.

2014

Hall,B., Phan,C. -M, Subbaraman,L., Jones,L. W., Forrest,J. Extraction versus in Situ techniques for measuring surface-adsorbed lysozyme. Optometry and Vision Science 2014;91,9:1062-1070. [ Show Abstract ]

PURPOSE: To compare two techniques for measuring the activity of lysozyme deposited onto hydrogel contact lens and to image the binding of Micrococcus lysodeikticus to contact lenses. METHODS: Using a previously described protein extraction technique and a recently developed in situ technique, we measured the time-dependent activity of adsorbed lysozyme on six different contact lens materials during the first minute and up to 1 week of interaction with the material surface. Total activity of extracted lysozyme, total in situ activity, and the activity of the outer surface layer of sorbed lysozyme were determined using the two different techniques. Micrococcal cellular interaction with surface-adsorbed lysozyme was imaged using confocal microscopy. RESULTS: The differences between total extracted activities, total in situ activities, and surface activities were both measurable and material specific. In most cases, total extracted activity is greater than total in situ activity, which, in turn, is greater than surface activity. After 1 week, etafilcon A had the highest extracted activity at 137 µg/lens, followed by omafilcon A, balafilcon A, comfilcon A, senofilcon A, and lotrafilcon B at 27.4, 2.85, 2.02, 0.46, and 0.27 µg/lens, respectively. Micrococcal cell adhesion was greatest on contact lenses with high contact angles, such as balafilcon A, omafilcon A, and senofilcon A and lowest on contact lenses with low contact angles, such as etafilcon A, comfilcon A, and lotrafilcon B. Subsequent removal/prevention of adhered micrococcal cells was greatest on balafilcon A, which had the highest surface activity, and lowest on lotrafilcon B, which had the lowest surface activity. CONCLUSIONS: This study has measured and made direct comparisons between two established techniques for measuring the activity of adsorbed lysozyme. The extraction technique determines the activity of underlying layers of lysozyme or lysozyme within the matrix of the material. Conversely, the in situ technique allows conclusions to be drawn about only the biologically relevant lysozyme including the activity of just the outer surface of adsorbed lysozyme. © American Academy of Optometry.

Phan,C. -M, Subbaraman,L. N., Jones,L. In vitro drug release of natamycin from ß-cyclodextrin and 2-hydroxypropyl-ß-cyclodextrin-functionalized contact lens materials. Journal of Biomaterials Science, Polymer Edition 2014;25,17:1907-1919. [ Show Abstract ]

Purpose: The antifungal agent natamycin can effectively form inclusion complexes with beta-cyclodextrin (ß-CD) and 2-hydroxypropyl-ß-cyclodextrin (HP-ßCD) to improve the water solubility of natamycin by 16-fold and 152-fold, respectively (Koontz, J. Agric. Food. Chem. 2003). The purpose of this study was to develop contact lens materials functionalized with methacrylated ß-CD (MßCD) and methacrylated HP-ßCD (MHP-ßCD), and to evaluate their ability to deliver natamycin in vitro. Methods: Model conventional hydrogel (CH) materials were synthesized by adding varying amounts of MßCD and MHP-ßCD (0, 0.22, 0.44, 0.65, 0.87, 1.08% of total monomer weight) to a monomer solution containing 2-hydroxyethyl methacrylate (HEMA). Model silicone hydrogel (SH) materials were synthesized by adding similar concentrations of MßCD and MHP-ßCD to N,N-dimethylacrylamide (DMAA)/10% 3-methacryloxypropyltris(trimethylsiloxy)silane (TRIS). The gels were cured with UV light, washed with ethanol and then, hydrated for 24 h (h). The model materials were then incubated with 2 mL of 100 g/mL of natamycin in phosphate buffered saline (PBS) pH 7.4 for 48 h at room temperature. The release of natamycin from these materials in 2 mL of PBS, pH 7.4 at 32 ± 2 °C was monitored using UV-vis spectrophotometry at 304 nm over 24 h. Results: For both CH and SH materials, functionalization with MßCD and MHP-ßCD improved the total amount of drugs released up to a threshold loading concentration, after which further addition of methacrylated CDs decreased the amount of drugs released (p < 0.05). The addition of CDs did not extend the drug release duration; the release of natamycin by all model materials reached a plateau after 12 h (p < 0.05). Overall, DMAA/10% TRIS materials released significantly more drug than HEMA materials (p < 0.05). The addition of MHP-ßCD had a higher improvement in drug release than MßCD for both HEMA and DMAA/10% TRIS gels (p < 0.05). Conclusions: A high loading concentration of methacrylated CDs decreases overall drug delivery efficiency, which likely results from an unfavorable arrangement of the CDs within the polymer network leading to reduced binding of natamycin to the CDs. HEMA and DMAA/10% TRIS materials functionalized with MHP-ßCD are more effective than those functionalized with MßCD to deliver natamycin.

Samsom,M., Chan,A., Iwabuchi,Y., Subbaraman,L., Jones,L., Schmidt,TA In vitro friction testing of contact lenses and human ocular tissues: Effect of proteoglycan 4 (PRG4). Tribology International 2014.

Phan,CM, Hui,A., Subbaraman,L., Jones,L. Insights to Using Contact Lenses for Drug Delivery. Clin Exp Pharmacol 2014;3,145:2161-1459. [ Show Abstract ]

There has been considerable interest in the potential application of contact lenses for ocular drug delivery. This short communication provides an overview of the challenges faced by delivering drugs using contact lenses, highlights the solutions to limitations that have already been achieved, and describes the barriers that remain before commercial application can be realized.

Phan,C. -M, Subbaraman,L., Jones,L. Contact lenses for antifungal ocular drug delivery: A review. Expert Opinion on Drug Delivery 2014;11,4:537-546. [ Show Abstract ]

Introduction: Fungal keratitis, a potentially blinding disease, has been difficult to treat due to the limited number of approved antifungal drugs and the taxing dosing regimen. Thus, the development of a contact lens (CL) as an antifungal drug delivery platform has the potential to improve the treatment of fungal keratitis. A CL can serve as a drug reservoir to continuously release drugs to the cornea, while limiting drug loss through tears, blinking, drainage and non-specific absorption. Areas covered: This review will provide a summary of currently available methods for delivering antifungal drugs from commercial and model CLs, including vitamin E coating, impregnated drug films, cyclodextrin-functionalized hydrogels, polyelectrolyte hydrogels and molecular imprinting. This review will also highlight some of the main factors that influence antifungal drug delivery with CLs. Expert opinion: Several novel CL materials have been developed, capable of extended drug release profiles with a wide range of antifungal drugs lasting from 8 h to as long as 21 days. However, there are factors, such as first-order release kinetics, effectiveness of continuous drug release, microbial resistance, ocular toxicity and potential complications from inserting a CL in an infected eye, that still need to be addressed before commercial applications can be realized. © Informa UK, Ltd.

Phan,C. -M, Subbaraman,L., Liu,S., Gu,F., Jones,L. In vitro uptake and release of natamycin Dex -b- PLA nanoparticles from model contact lens materials. Journal of Biomaterials Science, Polymer Edition 2014;25,1:18-31. [ Show Abstract ]

Purpose: To evaluate the uptake and release of the antifungal agent natamycin encapsulated within poly(D,L-lactide)-dextran nanoparticles (Dex-b-PLA NPs) from model contact lens (CL) materials. Methods: Six model CL materials (gel 1:poly(hydroxyethyl methacrylate, pHEMA); gel 2:85% pHEMA: 15% [Tris(trimethylsiloxy)silyl]-propyl methacrylate (TRIS); gel 3: 75% pHEMA: 25% TRIS; gel 4: 85% N,N dimethylacrylamide (DMAA): 15% TRIS; gel 5:75% DMAA: 25% TRIS; and gel 6: DMAA) were prepared using a photoinitiation procedure. The gels were incubated in: (1) natamycin dissolved in deionized (DI) water and (2) natamycin encapsulated within Dex-b-PLA NPs in dimethylsulfoxide/DI water. Natamycin release from these materials was monitored using UV-visible spectrophotometry at 304 nm over 7 d. Results: Natamycin uptake by all model CL materials increased between 1 and 7 d (p < 0.001). The uptake of natamycin-NPs was higher than the uptake of the drug alone in DI water (p < 0.05). Drug release was higher in materials containing DMAA than pHEMA (p < 0.05). All gels loaded with natamycin-NPs also released more drug compared to gels soaked with natamycin in DI water (p < 0.001). After 1 h, CL materials loaded with natamycin alone released 28-82% of the total drug release. With the exception of gel 6, this burst released was reduced to 21-54% for CL materials loaded with natamycin-NPs. Conclusions: Model CL materials loaded with natamycin-Dex-b-PLA NPs were able to release natamycin for up to 12 h under infinite sink conditions. DMAA-TRIS materials may be more suitable for drug delivery of natamycin due to the higher drug release observed with these materials. © 2013 Taylor & Francis.

2013

Weeks,A., Subbaraman,L. N., Jones,L., Sheardown,H. Physical entrapment of hyaluronic acid during synthesis results in extended release from model hydrogel and silicone hydrogel contact lens materials. Eye and Contact Lens 2013;39,2:179-185. [ Show Abstract ]

OBJECTIVES:: This study was designed to assess the duration of hyaluronic acid (HA) release from model contact lens materials when HA was physically incorporated into the hydrogel during synthesis and to assess the effects of the HA release on lysozyme sorption. METHODS:: Model conventional and silicone hydrogel contact lens materials containing HA of various molecular weights as a releasable wetting agent were prepared. The HA was released into phosphate-buffered saline and MilliQ water, and the release was monitored using ultraviolet spectroscopy. Hyaluronic acid release was quantified by enzyme-linked immunosorbent assay. The effect of the releasable HA on lysozyme sorption to the materials was also analyzed using 125-I-labeled protein. RESULTS:: Hyaluronic acid loaded into the materials using this method could be released from conventional hydrogel materials for 21 days; the model silicone hydrogels showed release of more than 7 weeks. With one exception, the releasable HA decreased lysozyme sorption. CONCLUSIONS:: Hyaluronic acid physically incorporated into contact lens materials during synthesis may therefore be released for extended periods of time of up to 7 weeks. Hyaluronic acid release leads to decreased protein adsorption in general. This method has potential for modification of conventional and silicone hydrogel lenses with releasable HA as a wetting agent. © 2013 Lippincott Williams & Wilkins.

Jones,L., Brennan,N. A., González-Méijome,J., Lally,J., Maldonado-Codina,C., Schmidt,T. A., Subbaraman,L., Young,G., Nichols,J. J. The TFOS International Workshop on Contact Lens Discomfort: Report of the contact lens materials, design, and care subcommittee. Investigative Ophthalmology and Visual Science 2013;54,11:TFOS37-TFOS70.

Ng,A., Heynen,M., Luensmann,D., Subbaraman,L. N., Jones,L. Impact of tear film components on the conformational state of lysozyme deposited on contact lenses. Journal of Biomedical Materials Research - Part B Applied Biomaterials 2013;101,7:1172-1181. [ Show Abstract ]

Purpose To investigate the impact of lactoferrin and lipids on the kinetic denaturation of lysozyme deposited on silicone and conventional hydrogel lenses, using a complex artificial tear solution (ATS). Methods Two silicone hydrogel lenses (AIR OPTIX AQUA; lotrafilcon B and ACUVUE OASYS; senofilcon A) and two conventional hydrogel lenses (ACUVUE 2; etafilcon A and PROCLEAR; omafilcon A) were incubated in four solutions: an ATS, ATS without lactoferrin, ATS without lipids, and ATS without lactoferrin and lipids. At various time points over a 28-day period, the percentage of active lysozyme per lens was determined using a fluorescence activity assay and an ELISA. Results After 28 days, the percentage of active lysozyme extracted from etafilcon A lenses in all solutions was significantly higher than all other lens materials (p 0.05). The inclusion of lipids in the ATS significantly increased the lysozyme denaturation on both silicone hydrogel materials (p 0.05). The inclusion of lipids in the ATS significantly increased the lysozyme denaturation on both silicone hydrogel materials (p 0.05). Conclusions Lactoferrin and lipids have an impact on the denaturation of lysozyme deposited onto silicone hydrogel contact lenses, while conventional hydrogel lenses were unaffected. Future in vitro studies should consider the impact of tear film components when investigating protein deposition and denaturation on contact lenses. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 1172-1181, 2013. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

Ng,A., Heynen,M., Luensmann,D., Subbaraman,L. N., Jones,L. Optimization of a fluorescence-based lysozyme activity assay for contact lens studies. Current eye research 2013;38,2:252-259. [ Show Abstract ]

Purpose: To optimize a fluorescence-based lysozyme activity assay to investigate the conformational state of lysozyme in solution and to determine the impact of extraction and evaporation procedures and the possible interference of contact lens materials on lysozyme activity. Methods: The fluorescence-based lysozyme activity assay, Enzchek (Molecular Probes Inc, Eugene, OR) which utilizes fluorescently quenched Micrococcus lysodeikticus, was compared to the gold standard, classical lysozyme turbidity assay, using four differently concentrated lysozyme samples (20, 10, 5.0 and 2.0 ng/µL). Furthermore, six differently concentrated lysozyme samples (2.0, 1.0, 0.5, 0.25, 0.125 and 0.01 µg/µL) were quantified using the fluorescence-based assay in the presence of extraction solvents consisting of 0.2% and 0.02% trifluroacetic acid/acetonitrile and following evaporation procedures. Results: A standard curve was generated by the fluorescence-based assay ranging from 2 to 150 ng. The total active lysozyme quantified in the four lysozyme samples was not significantly different between the two assays (p > 0.05) and the concordance correlation coefficient was determined to be 0.995. However an average discrepancy between the two assays was found to be 0.474 ng, with the turbidity assay typically reporting higher active lysozyme measurements. The sensitivity of the fluorescence-based assay was higher than the classical turbidity assay when quantifying 20 ng or less active lysozyme. Following the extraction and evaporation procedures and the addition of lens extracts, the total active lysozyme recovered was 95% or greater. Conclusions: In comparison to the classical turbidity assay, the fluorescence-based assay is a very sensitive method, making it a favorable technique, particularly when studying contact lens materials that deposit relatively low levels of lysozyme. © Informa Healthcare USA, Inc.

Phan,C. -M, Subbaraman,L. N., Jones,L. In vitro uptake and release of natamycin from conventional and silicone hydrogel contact lens materials. Eye and Contact Lens 2013;39,2:162-168. [ Show Abstract ]

OBJECTIVES:: To investigate the uptake and release of the antifungal ocular drug, natamycin from commercially available conventional hydrogel (CH) and silicone hydrogel (SH) contact lens (CL) materials and to evaluate the effectiveness of this delivery method. METHODS:: Five commercial SH CLs (balafilcon A, comfilcon A, galyfilcon A, senofilcon A, and lotrafilcon B) and four CH CLs (etafilcon A, omafilcon A, polymacon, vifilcon A) were examined in this study. These lenses were incubated with natamycin solubilized in dimethyl sulfoxide, and the release of the drug from these lenses, in Unisol 4 pH 7.4 at 32±1 C, was determined using UV-visible spectrophotometry at 305 nm over 24 hours. RESULTS:: There was a significant uptake of natamycin between 0 hour and 24 hours (P0.05). There was a significant difference in release between all the SH materials (P0.05). There was a significant difference in release between all the SH materials (P0.05). There was a significant difference in release between all the SH materials (P0.05). Overall, the release of natamycin was higher in CH than SH lenses (P<0.001). CONCLUSIONS:: All CLs released clinically relevant concentrations of natamycin within 30 minutes, but this release reached a plateau after approximately 1 hour. Further CL material development will be necessary to produce a slow and sustained drug releasing device for the delivery of natamycin. © 2013 Lippincott Williams & Wilkins.

2012

Weeks,A., Subbaraman,L. N., Jones,L., Sheardown,H. The competing effects of hyaluronic and methacrylic acid in model contact lenses. Journal of Biomaterials Science, Polymer Edition 2012;23,8:1021-1038. [ Show Abstract ]

The aim of this study was to determine the influence of hyaluronic acid (HA) on lysozyme sorption in model contact lenses containing varying amounts of methacrylic acid (MAA). One model conventional hydrogel (poly(2-hydroxyethyl methacrylate) (pHEMA)) and two model silicone hydrogels (pHEMA, methacryloxypropyltris(trimethylsiloxy)silane (pHEMA TRIS) and N,N-dimethylacrylamide, TRIS (DMAA TRIS)) lens materials were prepared with and without MAA at two different concentrations (1.7 and 5%). HA, along with dendrimers, was loaded into these model contact lens materials and then cross-linked with 1-ethyl-3-(3-dimethylamino propyl)-carbodiimide (EDC). Equilibrium water content (EWC), advancing water contact angle and lysozyme sorption on these lens materials were investigated. In the HA-containing materials, the presence (P < 0.05) and amount (P < 0.05) of MAA increased the EWC of the materials. For most materials, addition of MAA reduced the advancing contact angles (P < 0.05) and for all the materials, the addition of HA further improved hydrophilicity (P < 0.05). For the non-HA containing hydrogels, the presence (P < 0.05) and amount (P < 0.05) of MAA increased lysozyme sorption. The presence of HA decreased lysozyme sorption for all materials (P < 0.05). MAA appears to work synergistically with HA to increase the EWC in addition to improving the hydrophilicity of model pHEMA-based and silicone hydrogel contact lens materials. Hydrogel materials that contain HA have tremendous potential as hydrophilic, protein-resistant contact lens materials. © Koninklijke Brill NV, Leiden, 2012.

Subbaraman,L. N., Glasier,M. -A, Varikooty,J., Srinivasan,S., Jones,L. Protein deposition and clinical symptoms in daily wear of etafilcon lenses. Optometry and Vision Science 2012;89,10:1450-1459. [ Show Abstract ]

Purpose.: To determine the relationship between clinical signs and symptoms and protein deposition over 8 h of wear of etafilcon A lenses in symptomatic and asymptomatic contact lens wearers. Methods.: Thirty adapted soft contact lens wearers (16 symptomatic and 14 asymptomatic) were fitted with etafilcon A lenses. In vivo wettability, non-invasive tear break-up time, and subjective symptoms (vision, comfort, and dryness) were assessed at baseline and after 2, 4, 6, and 8 h. After 2, 4, 6, and 8 h time points, lenses were collected, and total protein, total lysozyme, and active lysozyme deposition were assessed. Results.: There was a significant reduction (p = 0.032) in the non-invasive tear break-up time at 8 h in both groups. In the symptomatic group, there was a significant reduction in subjective comfort and dryness ratings at 6 and 8 h measurement with respect to baseline (p 94% at 8 h). Pearson's correlations between subjective symptoms and protein deposition showed poor correlations for total protein/lysozyme and any subjective factor (r 0.05), and only weak correlations between dryness and % active lysozyme (r = 0.3 to 0.5 for all time points). However, stronger correlations were found between active lysozyme and subjective comfort (r = 0.6 to 0.7; p < 0.001). Conclusions.: In addition to investigating total protein deposited on contact lenses, it is of significant clinical relevance to determine the conformational state of the deposited protein. Copyright © 2012 American Academy of Optometry.

2011

Subbaraman,L. N., Borazjani,R., Zhu,H., Zhao,Z., Jones,L., Willcox,M. D. P. Influence of protein deposition on bacterial adhesion to contact lenses. Optometry and Vision Science 2011;88,8:959-966. [ Show Abstract ]

Purpose. The aim of the study is to determine the adhesion of Gram positive and Gram negative bacteria onto conventional hydrogel (CH) and silicone hydrogel (SH) contact lens materials with and without lysozyme, lactoferrin, and albumin coating. Methods. Four lens types (three SH-balafilcon A, lotrafilcon B, and senofilcon A; one CH-etafilcon A) were coated with lysozyme, lactoferrin, or albumin (uncoated lenses acted as controls) and then incubated in Staphylococcus aureus (Saur 31) or either of two strains of Pseudomonas aeruginosa (Paer 6294 and 6206) for 24 h at 37°C. The total counts of the adhered bacteria were determined using the H-thymidine method and viable counts by counting the number of colony-forming units on agar media. Results. All three strains adhered significantly lower to uncoated etafilcon A lenses compared with uncoated SH lenses (p 0.05). Lactoferrin coating on lenses increased binding (total and viable counts) of Saur 31 (p < 0.05). Lactoferrin-coated lenses showed significantly higher total counts (p < 0.05) but significantly lower viable counts (p < 0.05) of adhered P. aeruginosa strains. There was a significant difference between the total and viable counts (p < 0.05) that were bound to lactoferrin-coated lenses. Albumin coating of lenses increased binding (total and viable counts) of all three strains (p < 0.05). Conclusions. Lysozyme deposited on contact lenses does not possess antibacterial activity against certain bacterial strains, whereas lactoferrin possess an antibacterial effect against strains of P. aeruginosa. © 2011 American Academy of Optometry.

2010

Subbaraman,L. N., Jones,L. Kinetics of lysozyme activity recovered from conventional and silicone hydrogel contact lens materials. Journal of Biomaterials Science, Polymer Edition 2010;21,3:343-358.

2009

Chow,L. M., Subbaraman,L. N., Sheardown,H., Jones,L. Kinetics of in vitro lactoferrin deposition on silicone hydrogel and FDA group II and group IV hydrogel contact lens materials. Journal of Biomaterials Science, Polymer Edition 2009;20,1:71-82. [ Show Abstract ]

The aim of this study was to compare the kinetics of lactoferrin deposition on silicone hydrogel (SH) and conventional FDA group II and group IV hydrogel contact lens materials. Seven lens materials, two conventional (etafilcon A, FDA group IV; omafilcon A, FDA group II) and five SH (lotrafilcon A, lotrafilcon B, balafilcon A, galyfilcon A and senofilcon A), were incubated in 1 ml (125)I-labeled lactoferrin solution for time periods ranging from 1 h to 28 days. At the end of specified incubation periods radioactive counts were determined on the lenses using an Automatic Gamma Counter. There was a gradual increase in lactoferrin deposition on all the lenses across all time points. At the end of 28 days the amount of lactoferrin/lens in microg was 11.3 +/- 1.9 for etafilcon A, 6.8 +/- 2.0 for omafilcon A, 2.1 +/- 0.9 for lotrafilcon A, 3.1 +/- 1.0 for lotrafilcon B, 11.8 +/- 2.9 for balafilcon A, 5.4 +/- 1.1 for galyfilcon A and 5.6 +/- 0.6 for senofilcon A. After 28 days, etafilcon A and balafilcon A deposited lactoferrin to the greatest degree (P < 0.05), but these were not different from each other (P = 0.48), while lotrafilcon A and B deposited the least (P < 0.05 vs. other lenses; P = 0.57 with each other). Galyfilcon A, senofilcon A and omafilcon A (P < 0.05 compared with other lenses; P > 0.05 with each other) deposited intermediate levels of lactoferrin. We concluded that radiochemical analysis is a sensitive and effective technique to determine the small quantities of lactoferrin deposited on SH lenses. The kinetics of lactoferrin deposition on contact lens materials depend on the chemical structure of the lens material.

Luensmann,D., Zhang,F., Subbaraman,L., Sheardown,H., Jones,L. Localization of lysozyme sorption to conventional and silicone hydrogel contact lenses using confocal microscopy. Current eye research 2009;34,8:683-697. [ Show Abstract ]

PURPOSE: To investigate the distribution profile of hen egg lysozyme (HEL) through poly-2-hydroxyethyl methacrylate (pHEMA)-based lens materials and silicone hydrogel (SH) lens materials using confocal laser scanning microscopy (CLSM). METHODS: Five silicone SH materials (balafilcon A, lotrafilcon A, lotrafilcon B, galyfilcon A, senofilcon A) and four pHEMA-based materials (alphafilcon A, etafilcon A, omafilcon A, vifilcon A) were incubated in 1.9 mg/ml protein solution for 24 hours. The protein solution consisted of HEL, which was conjugated with either fluorescein isothiocyanate (FITC) or lucifer yellow VS dilithium salt (LY). CLSM (Zeiss LSM 510 META) identified the location of the fluorescently labeled protein by using 1 micro m depth scans through the lens. In a second experiment, lenses were incubated with 2% (125) I labeled HEL to determine the amount of deposited protein on each lens. Both techniques were combined to describe the individual HEL profiles. RESULTS: After the incubation in fluorescently labeled HEL, all pHEMA-based materials and the SH material balafilcon A accumulated protein throughout the entire lens material, while, for the SH lenses lotrafilcon A and lotrafilcon B, HEL was primarily detected on the lens surface alone. Differences in protein uptake pattern due solely to the two conjugated dyes were most apparent for the SH materials galyfilcon A and senofilcon A; HEL was detected throughout these lenses when conjugated with LY but accumulated primarily on the surface when conjugated with FITC. CONCLUSION: CLSM in combination with a radiolabel technique can describe both the location and degree of protein deposition on different contact lens materials.

Subbaraman,L. N., Glasier,M. A., Sheardown,H., Jones,L. Efficacy of an extraction solvent used to quantify albumin deposition on hydrogel contact lens materials. Eye and Contact Lens 2009;35,2:76-80. [ Show Abstract ]

OBJECTIVES: Extracting proteins from conventional hydrogel (CH) and silicone hydrogel (SH) contact lens materials using a mixture of trifluoroacetic acid/acetonitrile (TFA/ACN) is a well-established procedure for quantifying individual and total protein deposited on contact lenses. The purpose of this study was to determine the efficacy of TFA/ACN in extracting albumin from SH and a CH group IV lens material using an in vitro model. METHODS: One CH group IV lens material (etafilcon A) and five different SH lens materials (lotrafilcon A, lotrafilcon B, balafilcon A, galyfilcon A, and senofilcon A) were incubated in both simple albumin solution and a complex artificial tear protein solution containing 125I-labeled albumin. All the lens materials were incubated for 14 days at 37 degrees C with constant rotations. Following the incubation period, radioactive counts were determined and the lenses were placed in an appropriate volume of the extraction solvent. After the specified time, the lenses were removed and radioactive counts were determined again to calculate the amount of albumin remaining on the lenses post-extraction. RESULTS: Extraction efficiencies for albumin from the artificial tear protein solution were 97.2% +/- 2 for etafilcon A, 77.3% +/- 6.2 for lotrafilcon A, 73.5% +/- 5.6 for lotrafilcon B, 81.5% +/- 5.8 for balafilcon, 91.2% +/- 3.4 for galyfilcon A, and 89.2% +/- 3.4 for senofilcon A. Results were similar for the albumin extracted after incubating in the simple albumin solution. CONCLUSIONS: Although TFA/ACN is efficient at extracting albumin deposited on etafilcon lenses, it does not extract all the albumin that is deposited on SH lenses and alternative extraction procedures should be sought.

Subbaraman,L. N., Woods,J., Teichroeb,J. H., Jones,L. Protein deposition on a lathe-cut silicone hydrogel contact lens material. Optometry and Vision Science 2009;86,3:244-250. [ Show Abstract ]

PURPOSE: To determine the quantity of total protein, total lysozyme, and the conformational state of lysozyme deposited on a novel, lathe-cut silicone hydrogel (SiHy) contact lens material (sifilcon A) after 3 months of wear. METHODS: Twenty-four subjects completed a prospective, bilateral, daily-wear, 9-month clinical evaluation in which the subjects were fitted with a novel, custom-made, lathe-cut SiHy lens material. The lenses were worn for three consecutive 3-month periods, with lenses being replaced after each period of wear. After 3 months of wear, the lenses from the left eye were collected and assessed for protein analysis. The total protein deposited on the lenses was determined by a modified Bradford assay, total lysozyme using Western blotting and the lysozyme activity was determined using a modified micrococcal assay. RESULTS: The total protein recovered from the custom-made lenses was 5.3 +/- 2.3 microg/lens and the total lysozyme was 2.4 +/- 1.2 microg/lens. The denatured lysozyme found on the lenses was 1.9 +/- 1.0 microg/lens and the percentage of lysozyme denatured was 80 +/- 10%. CONCLUSIONS: Even after 3 months of wear, the quantity of protein and the conformational state of lysozyme deposited on these novel lens materials was very similar to that found on similar surface-coated SiHy lenses after 2 to 4 weeks of wear. These results indicate that extended use of the sifilcon A material is not deleterious in terms of the quantity and quality of protein deposited on the lens.

2008

Dalton,K., Subbaraman,L. N., Rogers,R., Jones,L. Physical properties of soft contact lens solutions. Optometry and Vision Science 2008;85,2:122-128. [ Show Abstract ]


Purpose. To investigate the physical properties of commercially available soft contact lens solutions.
Methods. The pH, osmolality, surface tension (ST), and viscosity of various soft contact lens solutions were measured at room temperature. Viscosity measurements were also taken at 34°C. The solutions examined were Opti-Free Express (OFX), Opti-Free RepleniSH (OFR), Complete Moisture Plus (COM), UltraCare (UC), ReNu MultiPlus, Sensitive Eyes, AOSept (AO), Clear Care, SoloCare Aqua, and SoftWear saline. The peroxide solutions were measured before and after neutralization.
Results. The pH of most solutions was close to neutral (range 7.00-7.36), except for OFX and neutralized AO and Clear Care. The osmolality values of most solutions were in the 275 to 310 mOsm/kg range. OFX exhibited a significantly lower osmolality (225 mOsm/kg; p < 0.001), whereas UC was significantly higher (329 mOsm/kg; p < 0.001). Neutralized AO and SoftWear saline had ST values of approximately 67 mN/m. OFX, OFR, and SoloCare Aqua exhibited low ST values in the 30 to 35 mN/m range. The remaining solutions exhibited intermediate ST values of approximately 40 mN/m. These three groupings were significantly different (p < 0.001). The average viscosity of most solutions at room temperature was between 0.95 and 1.26 cP, except for COM (3.02 cP; p < 0.001). At 34°C, the average viscosity of most solutions was between 0.70 and 0.83 cP, except for COM, which had a viscosity of 1.92 cP (p < 0.001). The un-neutralized peroxide solutions had very different pH and osmolality values from all the solutions that would directly contact the eye (p < 0.001). Their viscosity and ST values were similar (p = NS).
Conclusions. This study detailed many physical properties of soft lens solutions that are not readily available and indicated that certain properties vary significantly among these products.

Glasier,M. -A, Keech,A., Sheardown,H., Subbaraman,L. N., Jones,L. Conformational and quantitative characterization of lysozyme extracted from galyfilcon and senofilcon silicone hydrogel contact lenses. Current eye research 2008;33,1:1-11. [ Show Abstract ]

PURPOSE: To compare two solvents for retrieval of lysozyme deposited on a silicone hydrogel (SH) contact lens material galyfilcon A (GA; Acuvue Advance). METHODS: Two buffers used were 50:50 acetonitrile/0.02% trifluoroacetic acid (buffer 1) and 50:50 acetonitrile/50 mM NaOH (buffer 2). RESULTS: Extraction efficiency from GA lenses was 74% (buffer 1) and 83% (buffer 2). Buffer 2 decreased lysozyme activity > buffer 1. Ex vivo GA lenses showed total protein deposition of 2-16 microg/lens with total lysozyme deposition of 0.3-3.9 microg/lens. CONCLUSIONS: We have developed a low acid strength extraction buffer that can be used to efficiently extract active lysozyme protein from novel siloxane-based contact lens materials.

Glasier,M. -A, Subbaraman,L. N., Senchyna,M., Jones,L. A solid-phase assay for the quantitation of total protein eluted from balafilcon, lotrafilcon, and etafilcon contact lenses. Current eye research 2008;33,8:631-640. [ Show Abstract ]

PURPOSE: To compare two variations of a membrane-based protein assay utilizing Amido black (AB) detection with a commercially available 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde (CBQCA) assay for use in the quantitation of individual tear proteins, pooled human tear proteins, and protein extracted from ex vivo lotrafilcon A, balafilcon A, and etafilcon A contact lens materials. METHODS: Ex vivo contact lens extracts, pooled human tears, and individual tear proteins (human serum albumin (HSA), bovine lactoferrin, human secretory immunoglobulin A (sIgA), human lysozyme) were subjected to three solid-phase assays: AB on polyvinylidene difluoride (AB on PVDF) and AB on nitrocellulose (AB on NC) and the CBQCA assay. Micro-bicinchonic acid (micro-BCA) assay was also employed with lens extracts to determine total protein concentration. Individual and pooled tear proteins were referenced to a micro version of the quantitative ninhydrin protein assay. RESULTS: The CBQCA demonstrated the greatest overall sensitivity and lowest intra- and inter-assay variability. AB on NC demonstrated the most accurate ability to quantify total protein in pooled human tear samples, although it also displayed the greatest protein-to-protein variation using individual tear proteins. The CBQCA assay displayed the greatest cross-reactivity with unworn balafilcon and lotrafilcon lens extracts, whereas AB on NC demonstrated the least. AB on NC measured similar amounts of total protein in extracted ex vivo lenses as the CBQCA assay if background interference was subtracted from CBQCA values. AB on PVDF measured the lowest amount of deposited protein from ex vivo lenses. CONCLUSION: Both the AB on NC and CBQCA assays can be used to measure protein in extracts of lotrafilcon, balafilcon, and etafilcon lens materials.

2007

Subbaraman,L. N., Glasier,M. A., Senchyna,M., Sheardown,H., Jones,L. Extraction efficiency of an extraction buffer used to quantify lysozyme deposition on conventional and silicone hydrogel contact lens materials. Eye and Contact Lens 2007;33,4:169-173. [ Show Abstract ]

PURPOSE: Extracting lysozyme from Food and Drug Administration group IV etafilcon lenses by using 0.2% trifluoroacetic acid and acetonitrile (TFA/ACN) is a well-established procedure. TFA/ACN has been the extraction buffer of choice for extracting proteins from silicone hydrogel contact lenses. The purpose of this study was to determine the efficiency of TFA/ACN in extracting lysozyme from silicone hydrogel and etafilcon lenses by using an in vitro model. METHODS: ACUVUE 2, Focus NIGHT & DAY, O2 Optix, PureVision, and ACUVUE Advance lenses were incubated in simple lysozyme solution and a complex artificial tear solution consisting of multiple tear components containing lysozyme labeled with iodine 125. All the silicone hydrogel lenses were incubated for 28 days, whereas the ACUVUE 2 lenses were incubated for 7 days at 37 degrees C with constant rotation. After the incubation period, radioactive counts were determined, and the lenses were placed in an appropriate volume of the buffer for 24 hours in darkness. The lenses were removed from the buffer, and radioactive counts were determined again. RESULTS: Extraction efficiencies for lysozyme from the artificial tear solution were 97.2% +/- 1.2% for ACUVUE 2, 64.3% +/- 6.2% for Focus NIGHT & DAY, 62.5% +/- 5.6% for O2 Optix, 53.5% +/- 5.8% for PureVision, and 89.2% +/- 3.4% for ACUVUE Advance. Results were similar for the lysozyme extracted after incubating in the simple lysozyme solution. CONCLUSIONS: TFA/ACN is extremely efficient at extracting lysozyme deposited on etafilcon lenses. However, it does not extract all the lysozyme deposited on silicone hydrogel lenses, and alternative extraction procedures should be sought.

Suwala,M., Glasier,M. -A, Subbaraman,L. N., Jones,L. Quantity and conformation of lysozyme deposited on conventional and silicone hydrogel contact lens materials using an in vitro model. Eye and Contact Lens 2007;33,3:138-143. [ Show Abstract ]

PURPOSE: To determine the activity of hen egg lysozyme (HEL) deposited on conventional and silicone hydrogel contact lens materials by using an in vitro model. METHODS: ACUVUE 2 (etafilcon A), PureVision (balafilcon A), ACUVUE Advance (galyfilcon A), Focus NIGHT & DAY (lotrafilcon A), O2 Optix (lotrafilcon B), Proclear (omafilcon A), and ACUVUE OASYS (senofilcon A) contact lenses were deposited in vitro in a phosphate-buffered solution (PBS) containing 2 mg/mL HEL. Lenses were briefly rinsed in PBS to remove unbound material and extracted in a mixture of acetonitrile and trifluoroacetic acid. After lyophilization, extracts were examined for lysozyme activity by micrococcal assay and total protein by Western blot. RESULTS: In terms of total protein accumulation, ACUVUE 2 showed the most, with 1,800 microg per lens. Proclear was next, with 68 microg per lens, and Focus NIGHT & DAY showed the least, with 2 microg per lens. ACUVUE Advance, ACUVUE OASYS, and O2 Optix accumulated similar amounts of lysozyme, at approximately 6 microg per lens. Lysozyme deposited on ACUVUE 2 showed the greatest activity (91% +/- 5%), and this result was statistically different from all other lens types (P<0.001). Lysozyme deposited on Focus NIGHT & DAY (24% +/- 5%) and O2 Optix (23% +/- 11%) showed the lowest activity. Lysozyme deposits on other lens materials showed intermediate activity (ACUVUE Advance, 60% +/- 15%; ACUVUE OASYS, 51% +/- 9%; PureVision, 58% +/- 8%; and Proclear, 38% +/- 3%). CONCLUSIONS: Silicone hydrogel lenses acquire less lysozyme deposit than conventional group II (Proclear) or group IV (ACUVUE 2) lenses do, and the levels of activity of the lysozyme are highly variable between materials.

2006

Subbaraman,L. N., Bayer,S., Glasier,M. -A, Lorentz,H., Senchyna,M., Jones,L. Rewetting drops containing surface active agents improve the clinical performance of silicone hydrogel contact lenses. Optometry and Vision Science 2006;83,3:143-151. [ Show Abstract ]

PURPOSE: The purpose of this study was to investigate the impact of using a rewetting drop (RWD) containing surface active agents (OPTI-FREE RepleniSH; Alcon, Fort Worth, TX) on the clinical performance and protein deposition when using a continuous-wear (CW) silicone hydrogel (SH) contact lens. METHODS: Subjects wore lotrafilcon A SH lenses on a 30-day CW basis for two consecutive 1-month periods while inserting either 0.9% unpreserved unit-dose saline (control) or multidose OPTI-FREE RepleniSH (test RWD). Subjective comfort and symptoms were assessed after 2 and 4 weeks with each product. After 1 month of wear with each product, lenses were collected and analyzed in the laboratory for total protein, total lysozyme, and percentage of denatured lysozyme. RESULTS: Symptoms of dryness and comfort varied across the day regardless of drop type (p < 0.001) with dryness being maximal on waking, least in the middle of the day, and increased towards the evening. The test RWD provided greater comfort on insertion (p = 0.02), better visual quality (p < 0.01), and less mucous discharge on waking (p = 0.02) than the control product. Lysozyme deposition was significantly reduced after the use of the test RWD as compared to saline (0.73 +/- 0.5 microg/lens vs. 1.14 +/- 0.7 microg/lens; p < 0.001) as was total protein deposition (1.17 +/- 0.7 microg/lens vs. 1.86 +/- 0.8 microg/lens; p < 0.001). Lysozyme denaturation was also reduced with the use of the test RWD compared with the control (76 +/- 10% vs. 85 +/- 7%; p < 0.01). CONCLUSIONS: The use of a RWD containing surface active agents provided greater subjective satisfaction, reduced lysozyme and total protein deposition, and reduced denatured lysozyme than a RWD containing saline alone.

Subbaraman,L. N., Glasier,M. -A, Senchyna,M., Sheardown,H., Jones,L. Kinetics of in vitro lysozyme deposition on silicone hydrogel, PMMA, and FDA groups I, II, and IV contact lens materials. Current eye research 2006;31,10:787-796. [ Show Abstract ]

We sought to compare the kinetics of in vitro lysozyme deposition on silicone hydrogel (SH), polymethyl methacrylate (PMMA), and FDA groups I, II, and IV contact lenses. Lenses were incubated in 125I-labeled lysozyme for time periods ranging from 1 hr to 28 days, and radioactive counts were determined. SH lenses and PMMA deposited less lysozyme than conventional hydrogel lenses (p < 0.05). Lysozyme accumulation on group IV lenses reached a maximum on the seventh day and then plateaued, whereas on groups I, II, and SH lenses, deposition continued to increase across all time periods, reiterating that kinetics of lysozyme deposition is highly material dependent.

2005

Subbaraman,L. N., Glasier,M. -A, Senchyna,M., Jones,L. Stabilization of lysozyme mass extracted from lotrafilcon silicone hydrogel contact lenses. Optometry and Vision Science 2005;82,3:209-214. [ Show Abstract ]

PURPOSE: Lysozyme deposits extracted from lotrafilcon silicone hydrogel (SH) contact lens materials demonstrate a loss in total mass as a function of storage time when assessed by Western blotting. This loss represents a potential source of error when quantifying total lysozyme deposition on SH lenses. The purpose of this study was to devise a method whereby lysozyme mass would be preserved over time to allow for its accurate quantitation after its removal from SH lenses. METHODS: Lysozyme deposits from 12 human worn lotrafilcon lenses were extracted using a 50:50 mixture of 0.2% trifluoroacetic acid and acetonitrile. Extracts were lyophilized to dryness, then resuspended in either reconstitution buffer (10 mM Tris-HCl, 1 mM EDTA) or modified reconstitution buffer (reconstitution buffer + 0.9% saline). BIOSTAB Biomolecule Storage Solution (Sigma-Aldrich) was added to one half of the samples from each buffer group. One microliter of each of the samples was immediately subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blotting, whereas the remaining volume was aliquoted and stored at -20 degrees C or -70 degrees C and subjected to the same procedures after 48 h of storage. Comparison of lysozyme band intensity in stored vs. fresh samples enabled calculation of percentage mass loss of lysozyme. RESULTS: Samples stored at -20 degrees C in reconstitution buffer with no BIOSTAB demonstrated a 33% loss in mass over 48 h of storage. Identical samples stored at -70 degrees C in modified reconstitution buffer with BIOSTAB added demonstrated <1% loss in mass. Statistical analysis indicated that buffer composition (p < 0.001), storage temperature (p = 0.04), and addition of BIOSTAB (p < 0.001) were all important in controlling loss of mass over time. CONCLUSION: We have optimized a procedure whereby the extracted mass of lysozyme deposits found on lotrafilcon SH lenses can be preserved, thus enabling accurate quantitation after extraction and resuspension.

Abstracts

2016

Phan C, Bajgrowicz M, Subbaraman L, Jones L. Release of moxifloxacin from daily disposable contact lenses using an in vitro eye model: Impact of artificial tear fluid composition and mechanical rubbing. Invest Ophthalmol Vis Sci 2016;57: E-abstract 1474. [ PDF ]

Walther H, Phan C, Subbaraman L, Jones L. Cholesterol Penetration into Daily Disposable Contact Lenses Using a Novel In Vitro Eye-Blink Model. Invest Ophthalmol Vis Sci 2016;57: E-abstract 1476. [ PDF ]

Muntz A, Subbaraman L, Jones L. Is there an association between lid wiper epitheliopathy, lens type and contact lens discomfort?. Optom Vis Sci 2016;93: E-abstract 160047.

Subbaraman L, Omali N, Lada M, Canavan K, Fadli Z, Jones L. An in-vitro lipid uptake model to predict ex-vivo lipid depostion on worn silicone hydrogel contact lenses. Optom Vis Sci 2016;93: E-abstract 160099.

Qiao H, Phan C-M, Walther H, Subbaraman L, Jones L. Localizing lysozyme deposition on contact lenses using a novel in vitro eye model. Optom Vis Sci 2016;93: E-abstract 160100.

Walther H, Phan C-M, Qiao H, Liu Y, Subbaraman L, Jones L. In vitro eye model to simulate the impact of blinking on contact lens deposition and drug delivery. Optom Vis Sci 2016;93: E-abstract 160101.

Phan C-M, Walther H, Riederer D, Smith R, Subbaraman L, Jones L. Determination of the release of wetting agents from nelfilcon a using a novel in vitro eye model. Optom Vis Sci 2016;93: E-abstract 165114. [ PDF ]

Heynen M, Qiao H, Subbaraman L, Scales C, Riederer D, Fadli Z, Jones L. Location of non-polar lipids in monthly replacement silicone hydrogel contact lens materials. Optom Vis Sci 2016;93: E-abstract 166116. [ PDF ]

Subbaraman L, Suko A, Omali N, Riederer D, Scales C, Fadli Z, Jones L. Polar and non-polar lipid deposition on monthly replacement contact lens materials. Optom Vis Sci 2016;93: E-abstract 165119.

Subbaraman L, Omali N, Lada M, Canavan K, Fadli Z, Jones L. An in-vitro lipid uptake model to predict ex-vivo lipid deposition on worn silicone hydrogel contact lenses. TFOS conference, Montpelier, France, 2016.

2015

Phan C, Jones L, Subbaraman L, Bajgrowicz M. Release of fluconazole from daily disposable contact lenses using a novel in vitro eye model. Invest Ophthalmol Vis Sci 2015;56: E-abstract 3085.

McCanna D, Oh S, Seo J, Subbaraman L, Coles-Brennan C, Fadli Z, Jones L. Effect of Denatured Lysozyme on Human Corneal Epithelial Cells. Invest Ophthalmol Vis Sci 2015;56: E-abstract 3511. [ PDF ]

Subbaraman L, Ng A, Coles-Brennan C, Fadli Z, Jones L. Surface versus bulk activity of lysozyme deposited on soft contact lens materials. Invest Ophthalmol Vis Sci 2015;56: E-abstract 3168.

Muntz A, vanDoorn K, Subbaraman L, Jones L. Impression cytology of the lid wiper area. Invest Ophthalmol Vis Sci 2015;56: E-abstract 4432. [ PDF ]

Bajgrowicz M, Phan C, Subbaraman L, Jones L. Release of ciprofloxacin and moxifloxacin from daily disposable contact lenses using an in vitro eye model. Invest Ophthalmol Vis Sci 2015;56: E-abstract 6085. [ PDF ]

Dantam J, Heynen M, Dominici C, Subbaraman L, Coles-Brennan C, Fadli Z, Jones L. Qualitative asymmetric mapping of lysozyme deposited on various contact lens materials using confocal laser scanning microscopy. Invest Ophthalmol Vis Sci 2015;56: E-abstract 6091. [ PDF ]

Walther H, Subbaraman L, Jones L. Novel in vitro method to determine pre-lens tear break up time of hydrogel and silicone hydrogel contact lenses. Invest Ophthalmol Vis Sci 2015;56: E-abstract 6105. [ PDF ]

Babaei Omali N, Subbaraman L, Coles-Brennan, Fadli Z, Jones L. Selective uptake of lysozyme by various hydrogel contact lens materials. Invest Ophthalmol Vis Sci 2015;56: E-abstract 6109. [ PDF ]

vanDoorn K, Subbaraman L, Lemp J, Maissa C, Jones L. A device to model pollen deposition on contact lenses. Invest Ophthalmol Vis Sci 2015;56: E-abstract 6112. [ PDF ]

vanDoorn K, Subbaraman L, Lemp J, Maissa C, Jones L. Design and validation of a device for modeling pollen adhesion to contact lenses. BCLA Clinical Conference and Exhibition, 2015. [ PDF ]

Subbaraman L, McCanna D, Oh S, Ng A, Coles-Brennan C, Fadli Z, Jones L. Lysozyme activity on contact lenses and the impact of denatured lysozyme on human corneal epithelial cells. BCLA Clinical Conference and Exhibition, 2015. [ PDF ]

Jones L, Babaei Omali N, Heynen M, Coles-Brennan C, Fadli Z, Subbaraman L. Determining qualitative and quantitative uptake of lysozyme by various contact lens materials. BCLA Clinical Conference and Exhibition, 2015. [ PDF ]

Dantam J, Heynen M, Coles-Brennan C, Fadli Z, Subbaraman L.  Kinetics of lysozyme sorption by various contact lens materials over short time periods. BCLA Clinical Conference and Exhibition, 2015. [ PDF ]

McCanna D, Oh S, Seo J, Coles_brennan C, Fadli Z, Subbaraman L. In vitro evaluation of the effect of lysozyme coated contact lenses on cell viability and inflammatory response. BCLA Clinical Conference and Exhibition, 2015. [ PDF ]

vanDoorn K, Subbaraman L, Lemp J, Maissa C, Jones L. Reversibility of pollen adhesion to contact lenses. Optom Vis Sci 2015;92: E-abstract 150025.

Subbaraman L, Heynen M, McCanna D, Omali N, Jansen M, Fadli Z, Toubouti Y, Coles-Brennan C, Jones L . Impact of pigment presence in etafilcon A on in vitro interaction of lysozyme and impact on inflammatory biomarker release. Optom Vis Sci 2015;92: E-abstract 150097.

2014

McCanna D,Liu L, Seo J, Subbaraman L, Jones L. Assessment of the growth of Stenotrophomonas maltophilia, Elizabethkingia meningoseptica and Delftia acidovorans in contact lens cases and on recovery media. Invest Ophthalmol Vis Sci 2014;55: E-abstract 6051.

Phan C, Subbaraman L, Jones L. Delivery of natamycin using cyclodextrin functionalized contact lenses. Invest Ophthalmol Vis Sci 2014;55: E-abstract 4643. [ PDF ]

Walther H, Subbaraman L, Wettig S, Jones L. In vitro surface pressure measurements of various tear film lipids. Invest Ophthalmol Vis Sci 2014;55: E-abstract 43. [ PDF ]

Cheung S, Subbaraman L, Schmidt T, Jones L. Localization of full-length recombinant human proteoglycan 4 in commercial contact lenses using confocal microscopy. Invest Ophthalmol Vis Sci 2014;55: E-abstract 6059. [ PDF ]

Dantam, McCanna D, Subbaraman L, Lakkis C, Morgan P, Nichols J, Jones L. Microbial contamination of contact lens storage cases with the use of different contact lens care solutions and lens materials. Invest Ophthalmol Vis Sci 2014;55: E-abstract 4675. [ PDF ]

Subbaraman L, McCanna D, Lorentz H, Soong F, Salapatek A, Jones L. Tear Cytokines in Non-Dry Eye and Dry Eye Participants After Exposure to a Low Humidity Environmental Exposure Chamber. Invest Ophthalmol Vis Sci 2014;55: E-abstract 3682.

Soong F, Lorentz H, Subbaraman L, Jones L, Salapatek A. The Controlled Low Humidity Environmental Exposure Chamber (LH-EEC) is a sensitive and specific tool for study of the Signs and Symptoms of Dry Eye (DE) versus Non-Dry Eye (NDE) Participant. Invest Ophthalmol Vis Sci 2014;55: E-abstract 2016.

Jones L, Dantam J, McCanna D, Subbaraman L, Morgan P, Nichols J, Lakkis C. Impact of different contact lens care solutions and lens materials on contact lens storage case contamination. BCLA Clinical Conference and Exhibition, 2014. [ PDF ]

Subbaraman L, Stahl U, Heynen M, Babaei Omali N, Canavan K, Jones L. Is there a difference in tear film and meibum composition in asymptomatic adapted contact lens and spectacle wearers?. BCLA Clinical Conference and Exhibition, 2014. [ PDF ]

Schulze M, Subbaraman L, Babaei Omali N, Stahl U, Canavan K, Jones L. Is there a difference between clinical signs and symptoms in asymptomatic adapted contact lens and spectacle wearers?. BCLA Clinical Conference and Exhibition, 2014. [ PDF ]

Subbaraman L, Babaei Omali N, Heynen M, Lada M, Canavan K, Jones L. Could lipid deposition on contact lenses be beneficial?. BCLA Clinical Conference and Exhibition, 2014.

Babaei Omali N, Subbaraman L, Heynen M, Thangavelu M, Dare E, Canavan K, Fadli Z, Jones L. Protein Deposition on Senofilcon A Contact Lenses in Symptomatic and Asymptomatic Lens Wearers. Optom Vis Sci 2014;91: E-abstract 145186. [ PDF ]

Babaei Omali N, Subbaraman L, Schulze M, Heynen M, Canavan K, Fadli Z, Jones L. Clinical Signs, Symptoms, Tear Film and Meibum Composition in Asymptomatic Senofilcon A Contact Lens and Spectacle Wearers. Optom Vis Sci 2014;91: E-abstract 145185. [ PDF ]

Subbaraman L, Babaei Omali N, Heynen M, Lakkis C, Morgan P, Bertsen D, Nichols J, Jones L. Impact of different lens care solutions on protein deposition on various soft contact lenses: A multicenter study. Optom Vis Sci 2014;91: E-abstract 140057.

Lorentz H, McCanna D, Subbaraman L, Jones L, Salapatek A, Soong F. Changes in cytokine expression for dry eye and non dry eye subjects exposed to a low humidity environmental exposure chamber. Optom Vis Sci 2014;91: E-abstract 140106.

2013

Hall B, Phan C, Subbaraman L, Jones L. Forrest J. Direct comparison between in situ versus extraction techniques for measuring absorbed proteins: Application to lysozome deposited onto hydrogel contact lenses. Invest Ophthalmol Vis Sci 2013;54: E-Abstract 5467.

Subbaraman L, Walther H, Kay L, Jones L. In vitro efficiency of contact lens care solutions in removing cholesterol deposits from silicone hydrogel contact lenses. Contact Lens & Anterior Eye 2013;36,S2:e41.

Subbaraman L, Thangavelu M, McCanna, Jones L. A novel, multiplex electrochemiluminescent technique to quantify tear film inflammatory markers. Contact Lens & Anterior Eye 2013;36,S2:e45.

Dare E, Subbaraman L, Jones L. Effects of environmental changes on in vitro corneal epithelial wound healing. Contact Lens & Anterior Eye 2013;36,S2:e20.

Woods J, Subbaraman L, Jones L. In-vitro wettability of four silicone hydrogel lenses with differing surface properties. Contact Lens & Anterior Eye 2013;36,S2:e29.

Subbaraman L, Mistry R, Thangavelu M, Jones L. Quantification of lipocalin-1 in tears and contact lens deposits using a sandwich ELISA technique. Contact Lens & Anterior Eye 2013;36,S2:e45-e46.

Phan C, Subbaraman L, Jones L. Delivery of natamycin using cyclodextrin functionalized contact lenses. NSERC 20/20 Meeting, 2013.

Phan C, Subbaraman L, Liu S, Gu F, Jones L. Drug delivery of natamycin from contact lens materials using Dex-b-PLA nanoparticles. ISCLR conference, Kyoto, Japan, 2013.

Jones L, Brennan N, Gonzalez-Meijome, Lally J, Maldonado-Codina C, Schmidt T, Subbaraman L, Young G. Contact lens materials, design and solutions: Relationship to contact lens discomfort. Tear Film & Ocular Surface Society meeting, Seattle, US, 2013.

Phan C, Subbaraman L, Liu S, Gu F, Jones L. In vitro uptake and release of natamycin Dex-b-PLA nanoparticles from silicone hydrogel contact lens materials. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Walther H, Subbaraman L, Jones L. Method optimization to quantify oxidative stress in tear film lipids. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

McCanna D, Chang J, Subbaraman L, Jones L. Efficacy of contact lens solutions against Achromobacter xylosoxidans biofilms using confocal microscopy. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Subbaraman L, Thangavelu M, McCanna D, Jones L. Tear film cytokine analyses using a novel electrochemiluminescent array technique. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Subbaraman L, Thangavelu M, McCanna D, Jones L. Quantification of lipocalin-1 in tears and contact lens deposits using a sandwich elisa technique. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Hall B, Phan C, Subbaraman L, Jones L, Forrest J. Extraction versus in situ techniques for measuring surface adsorbed lysozyme. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Dare E, Subbaraman L, Jones L. Impact of environmental changes on in vitro corneal epithelial wound healing. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Subbaraman L, Thangavelu M, McCanna D, Jones L. Quantifying tear film inflammatory markers using a novel, multiplex electrochemiluminescent technique. Tear Film & Ocular Surface International Conference, Sicily, Italy, 2013.

McCanna D, Chang J, Subbaraman L, Jones L. Efficacy of contact lens solutions against Achromobacter xylosoxidans biofilms using confocal microscopy. Tear Film & Ocular Surface International Conference, Sicily, Italy, 2013.

Dare E, Subbaraman L, Jones L. Impact of environmental changes on in vitro corneal epithelial wound healing. Tear Film & Ocular Surface International Conference, Sicily, Italy, 2013.

Subbaraman L, Mistry R, Thangavelu M, Jones L. Quantification of lipocalin-1 in tears and contact lens deposits using a sandwich elisa technique. Tear Film & Ocular Surface International Conference, Sicily, Italy, 2013.

Subbaraman L, Martell E, Heynen M, Ng A, Jones L. Kinetic activity of lysozyme when exposed to two differing contact lens care systems. Optom Vis Sci 2013;90: E-Abstract 130015.

McCanna D, Chang J, Subbaraman L, Jones L. Efficacy of contact lens solutions against Achromobacter xylosoxidans biofilms using confocal microscopy. Invest Ophthalmol Vis Sci 2013;54: EAbstract 523.

Walther H, Subbaraman L, Jones L. Efficacy of multi-purpose solutions in removing cholesterol desposits from silicone hydrogel contact lenses. Invest Ophthalmol Vis Sci 2013;54: E-Abstract 517.

Phan C, Subbaraman L, Jones L, Liu S, Gu F. In vitro uptake and release of natamycin dex-b-pla nanoparticles from silicone hydrogel contact lens materials. Invest Ophthalmol Vis Sci 2013;54: E-Abstract 501.

Subbaraman L, Thangavelu M, McCanna D, Jones L. Tear film cytokine analyses using a novel electrochemiluminescent array technique. Invest Ophthalmol Vis Sci 2013;54: E-Abstract 4325.

2012

Walther H, Subbaraman L, Jones L. In Vitro Dehydration of Daily Disposable and Silicone Hydrogel Contact Lens Materials . Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 6121.

Menzies K, Subbaraman L, Jones L. In vitro wettability comparison of hydrogel and silicone hydrogel daily disposable and frequent replacement contact lenses. Optom Vis Sci 2012;89:E-abstract 125032.

Ng A, Heynen M, Subbaraman L, Jones L. Optimization of a novel fluorescent based lysozyme activity assay for contact lens studies. Optom Vis Sci 2012;89:E-abstract 120052.

Subbaraman LN. What influences contact lens-related dry eye?. Netherlands Contact Lens Congress (Amsterdam, Netherlands), 2012.

Subbaraman LN. Bacterial adhesion to contact lens materials. Netherlands Contact Lens Congress (Amsterdam, Netherlands), 2012.

Subbaraman LN. Contact lens multipurpose solutions composition. Netherlands Contact Lens Congress (Amsterdam, Netherlands), 2012.

Subbaraman L, Sheardown H, Jones L. 2. Incorporating novel agents to improve the wettability of contact lens materials. Materials Science and Chemistry of Contact Lenses, New Orleans, 2012.

Phan C, Jacob J, Subbaraman L, Jones L. Visualizing the uptake and release of natamycin from commercial contact lenses using confocal microscopy. 2020 NSERC ophthalmic materials conference, Burlington, Canada, 2012.

2011

Subbaraman LN, Schmidt TA, Sheardown H. Incorporation of a glycoprotein to enhance wettability of conventional and silicone hydrogel contact lenses. NSERC 2020 Network Meeting (Orillia, Ontario), 2011.

Subbaraman LN. Silicone: the best and worst material for a soft contact lens. Ontario Opticians Association (Toronto, Canada), 2011.

2009

Subbaraman L, Jones L. In vitro wettability of surface modified and non-surface modified silicone hydrogel contact lens materials. Contact Lens & Anterior Eye 2009;32,5:240.

Subbaraman L, Jones L, Zhao Z, Zhu H, Willcox M. Bacterial adhesion to lysozyme-coated conventional and silicone hydrogel contact lens materials. Contact Lens & Anterior Eye 2009;32,5:229.

Subbaraman L, Jones L, Borazjani R, Zhao Z, Zhu H, Willcox M. Bacterial adhesion to lactoferrin-coated conventional and silicone hydrogel contact lens materials. International Society of Contact Lens Research (ISCLR) Meeting (Crete), 2009.

Subbaraman L, Jones L, Zhao Z, Zhu H, Willcox MDP. Bacterial adhesion to protein-coated conventional and silicone hydrogel contact lens materials. Ivey Institute Research Day (London, Ontario), 2009.

Subbaraman LN, Jones L, Borazjani R, Zhao Z, Zhu H, Willcox MDP. Bacterial adhesion to proteincoated conventional and silicone hydrogel contact lens materials. 15th Scientific Meeting of the International Society for Contact Lens Research (Crete, Greece), 2009.

Subbaraman LN, Jones L. In vitro wettability of surface modified and non-surface modified silicone hydrogel contact lens materials. Optom Vis Sci 2009;86:E-abstract 095754.

Subbaraman L, Jones L, Borazjani R, Zhao Z, Zhu H, Willcox M. Bacterial adhesion to lactoferrin-coated conventional and silicone hydrogel contact lens materials. Optom Vis Sci 2009;86:E-abstract 090758.

2008

Jones L, Subbaraman L. In vitro wettability of a non surface modified silicone hydrogel contact lens material. Contact Lens & Anterior Eye 2008;31,5:262.

Subbaraman L, Chow L, Sheardown H, Jones L. Lactoferrin uptake kinetics on silicone hydrogel and conventional hydrogel contact lens materials. Optom Vis Sci 2008;85: E-Abstract 085047.

Subbaraman L, Jones L, Zhao Z, Zhu H, Willcox M. Bacterial adhesion to lysozyme-coated conventional and silicone hydrogel contact lens materials. Optom Vis Sci 2008;85:E-abstract 80108.

Subbaraman L, Chow L, Sheardown H, Jones L. Kinetics of in vitro lactoferrin deposition on FDA group II, FDA group IV and silicone hydrogel contact lens materials. Invest Ophthalmol Vis Sci 2008;49: E-abstract 2022.

Jones L, Subbaraman L, Glasier MA, Dumbleton K. Quantification of protein deposition on five commercially available silicone hydrogel contact lens materials. Contact Lens & Anterior Eye 2008;31,5:263.

Jones L, Subbaraman L, Woods J. Protein deposition on a novel lathe-cut silicone hydrogel contact lens material (sifilcon A). Contact Lens & Anterior Eye 2008;31,5:262.

2007

Subbaraman L, Jones L. Activity of lysozyme deposited on conventional and silicone hydrogel contact lenses as a function of time. Invest Ophthalmol Vis Sci 2007;47:E-Abstract 5393.

Subbaraman L, Jones L. An in vitro comparison of the activity of lysozyme recovered from contact lens materials as a function of time. Optom Vis Sci 2007;84:E-abstract 075141.

Subbaraman L, Jones L. In vitro wettability of a non-surface-modified silicone hydrogel contact lens material. Optom Vis Sci 2007;84:E-abstract 075172.

Subbaraman L, Glasier MA, Dumbleton K, Jones L. Quantification of protein deposition on five commercially available silicone hydrogel contact lens materials. Optom Vis Sci 2007;84:E-abstract 070031.

Subbaraman L, Woods J, Jones L. Protein deposition on a novel lathe-cut silicone hydrogel contact lens material (sifilcon A). Optom Vis Sci 2007;84:E-abstract 070038.

Jones L, Subbaraman LN, Varikooty J, Srinivasan S, Glasier M. Activity of lysozyme deposited on oneday etafilcon contact lenses is correlated with subjective comfort. 14th Scientific Meeting of the International Society for Contact Lens Research (Whistler, Canada), 2007.

Subbaraman L, Jones L. In vitro wettability of a non surface modified silicone hydrogel contact lens material. 6th Canadian Optometry Conference on Vision Science (Waterloo, Ontario), 2007.

Jones L, Subbaraman L. Kinetics of lysozyme activity recovered from conventional and silicone hydrogel lenses. Contact Lens & Anterior Eye 2007;30,5:284-285.

Jones L, Subbaraman L, Srinivasan S, Varikooty J, Glasier M. Subjective comfort is correlated with the activity of lysozyme recovered from one-day etafilcon lenses. British Contact Lens Association Annual Meeting, Manchester, England, 2007.

Varikooty J, Srinivasan S, Chan A, Subbaraman L, Woods C, Simpson T, Jones L, Fonn D. Clinical manifestations of upper lid staining in adapted silicone hydrogel lens wearers. British Contact Lens Association Annual meeting (Manchester, UK), 2007.

Dalton K, Subbaraman L, Rogers R, Jones L. Physical properties of soft contact lens solutions. 6th Canadian Optometry Conference on Vision Science, Waterloo, Ontario, 2007.

Lorentz H, Campbell F, Subbaraman L, Jones L. The impact of drop solution on the out of pack wettability of conventional and silicone hydrogel contact lens materials. 6th Canadian Optometry Conference on Vision Science, Waterloo, Ontario, 2007.

Subbaraman L, Jones L. An in vitro comparison of the activity of lysozyme recovered from contact lens materials as a function of time. 6th Canadian Optometry Conference on Vision Science, Waterloo, Ontario, 2007.

Subbaraman L, Jones L. In vitro wettability of a non-surface-modified silicone hydrogel contact lens material. 6th Canadian Optometry Conference on Vision Science, Waterloo, Ontario, 2007.

Keir N, Subbaraman L, Woods C, Jones L, Fonn D. Clinical impact of pre-soaking a silicone hydrogel lens in a MPS care solution on a group of symptomatic wearers. ISCLR meeting (Whistler, BC, Canada), 2007.

Subbaraman L, Jones L. Activity of lysozyme deposited on conventional and silicone hydrogel contact lenses as a function of time. ISCLR meeting (Whistler, BC, Canada), 2007.

Subbaraman L, Jones L. Determination of lysozyme activity recovered from conventional and silicone hydrogel contact lenses as a function of time. University of Waterloo Graduate Student Research Conference, 2007.

2006

Subbaraman L, Jones L, Srinivasan S, Varikooty J, Glasier MA. Activity of lysozyme deposited on one-day etafilcon contact lenses is correlated with subjective comfort. Optom Vis Sci 2006;83:E-Abstract 060091.

Varikooty J, Srinivasan S, Subbaraman L, Feng Y, Jones L, Simpson T, Fonn D. The influence of pre-soaking single-use etafilcon contact lenses on ocular comfort in symptomatic and asymptomatic contact lens wearers. Optom Vis Sci 2006;83:E-Abstract 065245.

Srinivasan S, Varikooty J, Subbaraman L, Chan A, Woods C, Simpson T, Jones L, Fonn D. Atypical manifestation of upper lid margin staining in silicone hydrogel lens wearers with symptoms of dry eye. Optom Vis Sci 2006;83:E-Abstract 065255.

Subbaraman L, Glasier MA, Senchyna M, Sheardown H, Jones L. Lysozyme uptake kinetics on PMMA, FDA groups I, II, IV and first & second generation silicone hydrogel contact lens materials. Optom Vis Sci 2006;83:E-Abstract 065258.

Suwala M, Glasier MA, Subbaraman L, Jones L. Quantity and conformation of lysozyme deposited on conventional and silicone hydrogel contact lens materials using an in vitro model. Optom Vis Sci 2006;83:E-Abstract 065259.

Subbaraman LN, Jones L, Srinivasan S, Varikooty J, Glasier MA. Clinical signs & symptoms and protein deposition in one day wear of etafilcon lenses in symptomatic and asymptomatic subjects. Invest Ophthalmol Vis Sci 2006;47: E-Abstract 2400.

Subbaraman L, Jones L, Srinivasan S, Varikooty J. Clinical signs & symptoms and protein deposition in one day wear of etafilcon lenses in symptomatic & asymptomatic subjects. British Contact Lens Association Annual Meeting, Birmingham, England, 2006.

Subbaraman LN, Jones L, Srinivasan S, Varikooty J, Glasier M. The role of protein deposition and surface wettability in symptoms of contact lens-induced dryness during one day wear of etafilcon lenses in symptomatic and asymptomatic subjects. Contact Lens & Anterior Eye 2006;29,4:194-195.

Subbaraman LN, Glasier M, Senchyna M, Sheardown H, Jones L. Comparison of in vitro lysozyme uptake kinetics on PMMA, Conventional Hydrogel and First & Second generation Silicone Hydrogel contact lens materials. Contact Lens & Anterior Eye 2006;29,4:195.

Subbaraman LN, Glasier MA, Srinivasan S, Varikooty J, Jones L. Correlation between clinical signs & symptoms and protein deposition in one day wear of etafilcon lenses in symptomatic and asymptomatic subjects. University of Waterloo Graduate Student Research Conference, 2006.

Varikooty J, Srinivasan S, Subbaraman L, Chan A, Woods C, Jones L, Simpson T, Fonn D. Clinical manifestations of upper lid staining in adapted silicone hydrogel lens wearers. Optom Vis Sci 2006;83:E-abstract 065256.

Subbaraman LN, Glasier MA, Senchyna M, Sheardown H, Jones L. Comparison of in vitro lysozyme uptake kinetics on PMMA, Conventional Hydrogel and First & Second generation Silicone Hydrogel contact lens materials. Biomaterials meeting (New Orleans, USA), 2006.

Subbaraman L, Glasier M, Senchyna M, Sheardown H, Jones L. Comparison of the in vitro lysozyme uptake kinetics on PMMA, conventional hydrogel and first and second generation silicone hydrogel contact lens materials. 13th Symposium on the Materials Science and Chemistry of Contact Lenses (New Orlean, USA), 2006.

Suwala M, Glasier M, Subbaraman LN, Jones L. Quantity and conformation of lysozyme deposited on conventional and silicone hydrogel contact lens materials using an in vitro model. Biomaterials meeting (New Orleans, USA), 2006.

Subbaraman L, Jones L, Srinivasan S, Varikooty J, Glasier MA. The relationship between protein deposition and clinical signs and symptoms in one day wear of etafilcon lenses in symptomatic and asymptomatic subjects. Canadian Student Health Research Forum (Winnipeg, Canada), 2006.

2005

Subbaraman L, Glasier MA, Senchyna M, Jones L. Kinetics of 1251-labelled lysozyme deposition on silicone hydrogel, FDA group II and group IV contact lenses. Optom Vis Sci 2005;82:E-abstract 050046.

Subbaraman LN, Glasier MA, Senchyna M, Jones L. Kinetics of in vitro lysozyme deposition on silicone hydrogel, group II and group IV contact lens materials. Invest Ophthalmol Vis Sci 2005;46:E-abstract 910.

Subbaraman L, Senchyna M, Jones L. Determination of in vitro lysozyme uptake kinetics on silicone hydrogel, FDA group II and FDA group IV hydrogel contact lens materials. 24th Canadian Biomaterials Society Conference (Waterloo, Ontario), 2005.

Subbaraman L, Senchyna M, Jones L. Kinetics of 1251-labelled lysozyme deposition on silicone hydrogel FDA Group II and Group IV contact lenses. 13th Scientific Meeting of the International Society for Contact Lens Research, Coolum, Australia, 2005.

Subbaraman L, Glasier M, Senchyna M, Jones L. Determination of lysozyme deposition on silicone hydrogel, group II and group IV contact lenses as a function of time. Graduate Student Research Conference (University of Waterloo, Ontario), 2005.

Subbaraman L, Glasier M, Senchyna M, Jones L. An in vitro comparison of the kinetics of lysozyme deposition on silicone hydrogel, group II and group IV contact lens materials. Graduate Student Research Conference, University of Waterloo, Ontario, 2005.

Subbaraman LN. Subjective and objective measures of corneal staining related to multipurpose care systems.

Subbaraman LN, Jones L, Srinivasan S, Varikooty J, Glasier M. The relationship between protein deposition and clinical signs & symptoms in one day wear of etafilcon lenses in symptomatic and asymptomatic subjects. Canadian Student Health Research Forum, 2005.

Subbaraman LN, Glasier MA, Senchyna M, Jones L. An in vitro comparison of the lysozyme uptake kinetics on first & second generation silicone hydrogel and conventional hydrogel contact lens materials. Institute for Ocular Biomaterials Research Meeting (Hamilton, Ontario), 2005.

Subbaraman L, Glasier M, Senchyna M, Jones L. An in vitro comparison of the kinetics of lysozyme deposition on silicone hydrogel, group II and group IV contact lens materials. British Contact Lens Association Annual Meeting (Brighton, England), 2005.

2004

Jones L, Bayer S, Senchyna M, Subbaraman L, Glasier M, Dumbleton K, Fonn D. Rewetting drops influence comfort and protein deposition on silicone hydrogel contact lenses. Optom Vis Sci 2004;81,12s:57.

Bayer S, Jones LW, Senchyna M, Subbaraman L, Glasier M, Dumbleton K, Fonn D. Effect of rewetting drops on comfort and protein deposition of silicone hydrogel (Focus Night&Day) contact lenses. Invest Ophthalmol Vis Sci 2004;45,4:s65.

Subbaraman LN, Senchyna M, Jones L. Stabilization of lysozyme mass extracted from silicone hydrogel contact lens materials. Invest Ophthalmol Vis Sci 2004;45:ARVO E-Abstract 1556.

Bayer S, Jones L, Senchyna M, Subbaraman L, Glasier M, Dumbleton K, Fonn D. Effect of rewetting drops on comfort and protein deposition of silicone hydrogel (Focus Night & Day) contact lenses. Invest Ophthalmol Vis Sci 2004;45ARVO E-Abstract 1575.

Subbaraman LN, Senchyna M, Jones L. Stabilization of lysozyme mass extracted from silicone hydrogel contact lens materials. Graduate Student Research Conference (University of Waterloo, Ontario), 2004.

2002

Subbaraman LN. Stereopsis and Luminance Disparity. 6th All India Optometry Conference (Kolkata, India), 2002.

Professional Publications

2016

Subbaraman L, Pruitt J, Jones L. Measuring Contact Lens Friction. Contact Lens Spectrum 2016;31,January:40-43.

Subbaraman L. Is contact lens deposition good or bad?. ContactLensUpdate.com 2016.

2015

Srinivasan S. Subbaraman L. Current Innovations in Contact Lens Materials. Review of Optometry 2015;February 15.

2014

Subbaraman L. Summary: Report of the Contact Lens Materials, Design and Care Subcommittee. ContactLensUpdate.com 2014.

2013

Subbaraman L, Sivak A. Characterizing the surface properties of a contact lens: A review. ContactLensUpdate.com 2013.

Subbaraman L, Srinivasan S. A Lens Fit for Dry Eye. Review of Cornea and Contact Lenses 2013 17-21.

2010

Jones L, Menzies K, Subbaraman L. Comfortable contact lenses: A case of Mission Impossible?. Contact Lens Spectrum 2010;25,7:45-48.

2009

Dalton K, Subbaraman L, Rogers R, Jones L. Physikalische eigenschaften von pflegelosungen fur weiche kontaklinsen. Die Kontaklinse 2009;415-20.

Subbaraman L, Jones L. What influences contact lens related dry eye?. Contact Lens Spectrum 2009;24,7:39-43.

2006

Jones L, Subbaraman L, Rogers R, Dumbleton K. Surface treatment, wetting and modulus of silicone hydrogels. Optician 2006;232,6067:28-34.

2002

Krishnakumar R, Sukumar S, Subbaraman LN, Srinivasan S. Variability in the measurement of Interpupillary Distance. The Indian Optician 200268-70.

Books

Sheardown H, Subbaraman L. Opthalmic Coatings. In: Coatings for Biomedical Applications, ed. Mike Driver. Woodhead Publishing Ltd. .