Please use the archived list on the right to look at past peer-reviewed articles.
Boone,A., Heynen,M., Joyce,E., Varikooty,J., Jones,L. Ex vivo protein deposition on bi-weekly silicone hydrogel contact lenses. Optometry and Vision Science 2009;86,11:1241-1249. [ Show Abstract ]
Purpose. This study investigated the protein deposition that occurs on daily wear silicone hydrogel (SH) lenses, after 2 weeks of wear. Methods. A total of 40 subjects were divided into equal groups, based on their habitual SH contact lens [CIBA Vision O2OPTIX (O2); Johnson & Johnson ACUVUE ADVANCE with HYDRACLEAR (ADV); Bausch & Lomb PureVision (PV); CIBA Vision Night & Day (ND)]. A randomized, double-masked, cross-over study was conducted in which subjects wore either their habitual SH material or Johnson & Johnson ACUVUE OASYS with HYDRACLEAR PLUS (OAS) for 2 weeks. At the end of the 2-week period, lenses were collected for analysis of total protein, total lysozyme, and percent denatured lysozyme. Results. Total protein was greatest for PV (33 ± 6 μg/lens), with other lenses depositing 0.05). Total lysozyme was also greatest for the PV lens (11 ± 3 μg/lens), with other lenses depositing 0.05). Total lysozyme was also greatest for the PV lens (11 ± 3 μg/lens), with other lenses depositing 0.05). Total lysozyme was also greatest for the PV lens (11 ± 3 μg/lens), with other lenses depositing 0.05). The percentage of lysozyme that was denatured was greatest for ND (90 ± 8%) and lowest for PV (23 ± 10%). The lysozyme extracted from ND and O2 lenses was significantly more denatured than that extracted from the other lens materials (p 0.05) or between ADV, OAS, and PV (p > 0.05). The amount of denatured lysozyme/lens was <3 μg/lens for all materials. Lysozyme as a percentage of the total protein deposited ranged from 32 (PV) to 6% (O2). Conclusions. This study confirms that all SH lenses deposit low levels of protein, and that the amount and percentage of denatured lysozyme can vary, depending on the overall surface charge of the material and absence or type of surface treatment. © 2009 American Academy of Optometry.
Boone,A., Hui,A., Jones,L. Uptake and release of dexamethasone phosphate from silicone hydrogel and FDA group I, II, and IV hydrogel contact lenses. Eye and Contact Lens 2009;35,5:260-267. [ Show Abstract ]
OBJECTIVES: To investigate the uptake and release kinetics of the synthetic glucocorticoid anti-inflammatory drug dexamethasone into various conventional and silicone hydrogel contact lens materials. METHODS: Three conventional and six silicone hydrogel lenses were used in this study. A 0.1% dexamethasone solution was formulated and used to dope the various contact lens materials. The uptake and release of the drug was measured using a UV-visible light spectrophotometer at various time points during a period of 24 hr for each phase. RESULTS: Statistical analysis showed that all lenses took up a significant amount of dexamethasone. Alphafilcon A and lotrafilcon A showed the greatest uptake of dexamethasone, at 118 +/- 10 microg/lens and 102 +/- 11 microg/lens, respectively, and galyfilcon took up the least amount of drug at 34 +/- 6 microg/lens. The release of the drug from the lens materials was also statistically significant. The majority of the lenses released between 20 and 30 microg/lens, except for alphafilcon A and lotrafilcon A, which released a statistically different amount of drug when compared with the other lens materials. Alphafilcon A released 65 +/- 1.3 microg/lens, whereas lotrafilcon A slowly released only 11 +/- 0.2 microg/lens. CONCLUSIONS: Although most of the lenses released enough drug to have anti-inflammatory action, none of the materials released drug for a long enough period of time to be clinically useful as a drug delivery device.
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.
Dumbleton,K., Woods,C., Fonn,D. An investigation of the efficacy of a novel ocular lubricant. Eye and Contact Lens 2009;35,3:149-155. [ Show Abstract ]
OBJECTIVE: To investigate the efficacy of a novel ocular lubricant compared with a commercially marketed ocular lubricant in a group of noncontact lens wearers currently using over-the-counter products for the management of symptoms of moderate to severe dry eye. METHODS: This was a prospective, double-masked study that randomized 110 subjects in a ratio of 1:1 to receive a novel ocular lubricant (test group) or a marketed ocular lubricant (control group). Subjects were instructed to instill the lubricant eye drops at least three times daily. After enrollment, subjects were evaluated at baseline and at 7 and 30 days. They were also required to complete a series of home-based subjective questionnaires after 15 days. Main outcomes were subjective symptoms and objective clinical assessment at 7 and 30 days. RESULTS: The test group had higher overall comfort ratings than the control group (P = 0.012). Seventy-one percent of the test group and 57% of the control group said the drops used "somewhat" or "definitely" improved ocular comfort; 62% of the test group had greater end-of-day comfort compared with 45% of the control group (P = 0.015). There were no between-group differences in visual acuity, tear quality or quantity, corneal staining, conjunctival staining, or bulbar and limbal conjunctival hyperemia. CONCLUSIONS: The novel ocular lubricant offers equivalent or superior comfort compared with a marketed lubricant eye drop. Objective clinical outcomes were not statistically significantly different between the two groups. © 2009 Lippincott Williams & Wilkins.
Dumbleton,K., Woods,C., Jones,L., Fonn,D., Sarwer,D. B. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement in the United States. Eye and Contact Lens 2009;35,4:164-171. [ Show Abstract ]
OBJECTIVE: The objectives of this study were to assess current recommendations for replacement frequency (RF) of silicone hydrogel (SH) and daily disposable (DD) lenses, to determine compliance with these recommendations, and to investigate the reasons given for noncompliance. METHODS: A package containing 20 patient surveys was sent to 309 eye care practitioners (ECPs) in the United States who had agreed to participate in the study. One thousand eight hundred fifty-nine completed surveys were received from 158 ECPs and 1,654 surveys were eligible for analysis. Questions related to patient demographics, lens type, lens wearing patterns, the ECP instructions for RF, and the actual patient reported RF. ECPs were asked to provide lens information and their recommendation for RF after the surveys had been completed and sealed in envelopes. All responses were anonymous. RESULTS: Sixty-six percent of patients were women and their mean age was 34 ± 12 years. Eighty-eight percent of lenses were worn for daily wear, 12.8 ± 3.2 hours a day, 6.2 ± 1.5 days a week. Lens type distribution was 16% DD, 45% 2 week (2W) SH, and 39% 1 month (1M) SH. ECP recommendations for RF varied according to the lens type; 1% of 1M (95% CI 0.2-1.7), 4% of DD (95% CI 2.1-7.2), and 18% of 2W (95% CI 15.1-20.7) patients were given instructions that did not conform to the manufacturers' recommended RF (MRRF). When considering only those patients who were given the correct instructions for RF, 38% were not compliant with the MRRF; noncompliance rates varied according to the lens type and were 12% for DD (95% CI 8.6-17.2), 28% for 1M (95% CI 24.9-32.1), and 52% for 2W (95% CI 47.8-55.8). The most frequent reasons for over wearing lenses were "forgetting which day to replace lenses" (51%) and "to save money" (26%). Fifty-three percent believed that a reminder system would aid compliance; the most popular methods being a cell phone reminder or text message (29%) and a nominated day each week or month (26%). Discussions between the ECPs and the patients were more extensive for patients who were compliant with the MRRF. CONCLUSIONS: ECPs recommended RFs more frequently with DD and 1M SH lenses than with 2W SH lenses, consistent with manufacturers' recommendations. Patients were less compliant with RF than ECPs for all lens types investigated. Patients were most compliant with RF when wearing DD lenses and least compliant when wearing 2W SH lenses. Better communication facilitated greater compliance with RF. More than half of those not replacing lenses, when recommended, reported that this was because they forgot which day to replace their lenses. © 2009 Lippincott Williams & Wilkins, Inc.
Keech,A., Flanagan,J., Simpson,T., Jones,L. Tear meniscus height determination using the OCT2 and the RTVue-100. Optometry and Vision Science 2009;86,10:1154-1159. [ Show Abstract ]
PURPOSE: To compare anterior segment spectral-domain optical coherence tomography (SOCT) tear meniscus height (TMH) measures with those from the more commonly used time-domain OCT (TOCT). METHODS: The right eye of 50 healthy subjects had images of their TMH captured with TOCT (OCT2) and SOCT (RTVue-100). Data were acquired using two different anterior segment lenses, the cornea/anterior module-short (CAM-S) and long (CAM-L), on the SOCT. Images were then analyzed for differences in their derived TMH. RESULTS: The average TMH for TOCT was 0.280 ± 0.139 mm, whereas the mean TMH measured using the SOCT was 0.354 ± 0.163 mm and 0.345 ± 0.167 mm for the CAM-S and CAM-L, respectively. There was a significant difference (p < 0.001) when comparing TOCT with either of the SOCT lenses. There was no statistically significant difference between the CAM-L and CAM-S (p = 1.0). Bland-Altman analysis showed poor agreement between TOCT and SOCT (95% limits of agreement -0.138 to + 0.285 mm for the CAM-S and -0.185 to +0.315 mm for the CAM-L). CONCLUSIONS: The RTVue-100 produces TMH measurements that are significantly higher than OCT2 in a normal patient population. However, the RTVue-100 showed a number of other advantages over the OCT2 in the measurement and analysis of images. Future work needs to determine the causative factors behind the observed differences.
Keir,N. J., Simpson,T., Jones,L. W., Fonn,D. Wavefront-guided LASIK for myopia: Effect on visual acuity, contrast sensitivity, and higher order aberrations. Journal of Refractive Surgery 2009;25,6:524-533. [ Show Abstract ]
PURPOSE: To determine the impact of wavefrontguided LASIK for myopia with or without astigmatism on high and low contrast best spectacle-corrected visual acuity (BSCVA), photopic and mesopic contrast sensitivity, and higher order aberrations. METHODS: Bilateral wavefront-guided LASIK (LADARVision4000; Hansatome microkeratome) was performed on 324 eyes (162 patients) with a mean spherical manifest refraction of -2.84±1.35 diopters (D) (range: -0.25 to -6.50 D) and astigmatism of -0.81±0.74 D (range: 0 to -4.00 D). Mean age was 37.7±9.3 years (range: 20 to 60 years). Best spectacle-corrected visual acuity and contrast sensitivity were assessed using ETDRS charts and vertical sinusoidal gratings, respectively. Higher order aberrations were measured using a Shack-Hartmann wavefront sensor, analyzed across a 5-mm pupil. Repeated measures and post hoc analyses determined statistical significance (P<.0025). Only right eyes were analyzed. RESULTS: One hundred thirty-six eyes (84%) had uncorrected visual acuity of 20/20 or better 6 months postoperative; 80.9% (131 eyes) were within ±0.50 D of attempted correction. Statistically significant postoperative improvements were noted in high and low contrast BSCVA (both P≤.001); in photopic contrast sensitivity at 3, 6, and 12 cycles per degree (cpd); and in mesopic contrast sensitivity at 12 and 18 cpd (all P<.001). With respect to higher order aberrations, a statistically significant change was seen in Zernike coefficients Z 3 -1, Z 3 1, Z 3 -3, Z 3 3, and Z 3 4 following surgery (range of mean absolute change: 0.042 to 0.142 μm; all P<.001). All increased in magnitude except for Z 3 -3, which decreased. CONCLUSIONS: Despite an increase in higher order aberrations, wavefront-guided LASIK yields excellent visual acuity and contrast sensitivity. Spherical aberration, which increases the most following non-wavefront-guided LASIK, showed no significant change.
Luensmann,D., Heynen,M., Liu,L., Sheardown,H., Jones,L. Determination of albumin sorption to intraocular lenses by radiolabeling and confocal laser scanning microscopy. Journal of cataract and refractive surgery 2009;35,11:2000-2007. [ Show Abstract ]
Purpose: To determine albumin adsorption profiles and penetration depth of 3 intraocular lens (IOL) materials over time using confocal laser scanning microscopy (CLSM) and radiolabeling. Setting: Centre for Contact Lens Research, School of Optometry, and Department of Biology, University of Waterloo, Waterloo, Ontario, Canada. Methods: Poly(methyl methacrylate) (PMMA), silicone, and foldable hydrophilic acrylic IOLs were incubated in 0.5 mg/mL bovine serum albumin (BSA) for 1, 7, and 14 days. The BSA was conjugated with lucifer yellow VS to allow identification of the protein location by fluorescent imaging with CLSM. Next, the protein uptake was quantified using 2% 125I-labeled BSA. Results: Confocal laser scanning microscopy showed increasing BSA uptake for silicone and PMMA IOLs after 14 days of incubation (P<.05), with an apparent penetration depth of 8.7 μm ± 1.9 (SD) and 9.2 ± 1.4 μm, respectively. For hydrophilic acrylic IOLs, BSA was detected at a depth of 38 ± 7.4 μm after 1 day, followed by an increase to 192.7 ± 16.2 μm after 14 days. Despite the penetration depth into the hydrophilic acrylic IOLs, quantitative results confirmed that PMMA and hydrophilic acrylic deposited significantly less BSA (mean 278.3 ± 41.7 ng and 296.5 ± 33.1 ng, respectively) than silicone IOLs (mean 392.6 ± 37.6 ng) (P<.05). Conclusions: Silicone and PMMA IOL materials showed BSA sorption near the lens surface only, while BSA penetrated deep into the hydrophilic acrylic IOL matrix. Combining the qualitative CLSM method and quantitative radiolabeling technique provided detailed information on protein interactions with implantable biomaterials. © 2009 ASCRS and ESCRS.
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.
Ngo,W., Heynen,M., Joyce,E., Jones,L. Impact of protein and lipid on neutralization times of hydrogen peroxide care regimens. Eye and Contact Lens 2009;35,6:282-286. [ Show Abstract ]
Purpose: To investigate the effect of protein, lipid, and lens material on the neutralization kinetics of one-step hydrogen peroxide disinfection systems. Methods: A UV-based assay was used to determine the rate of neutralization of three one-step hydrogen peroxide systems (CIBA Vision Clear Care; CIBA Vision AOSEPT; Abbott Medical Optics UltraCare). Protein (bovine serum albumin and lysozyme) and various lipids were added to the lens cases during the neutralization phase to determine whether they influenced the rate of neutralization. Finally, rates were determined when the cases contained a silicone hydrogel lens material (lotrafilcon A) or Food and Drug Administration group IV (etafilcon A) lenses. Results: Neutralization for all three systems was complete within 90 minutes. The rate of neutralization for Clear Care and AOSEPT were not significantly different from each other (P=NS). UltraCare exhibited statistically higher levels of peroxide up to the 20-minute time point (P<0.001) Protein, lipid, or lens material did not significantly affect the rate of neutralization for any regimen (P=NS). Conclusions: Tablet-based one-step disinfection systems neutralize at a slower rate than disc-based peroxide systems, but this difference is only significant during the first 20 minutes after the onset of neutralization. Neither lens deposition nor lens material plays a role in the speed of neutralization of peroxide-based systems. © 2009 Lippincott Williams & Wilkins.
Papas,E. B., Decenzo-Verbeten,T., Fonn,D., Holden,B. A., Kollbaum,P. S., Situ,P., Tan,J., Woods,C. Utility of short-term evaluation of presbyopic contact lens performance. Eye and Contact Lens 2009;35,3:144-148. [ Show Abstract ]
OBJECTIVES: To establish if evaluations of multifocal contact lens performance conducted at dispensing are representative of behavior after a moderate adaptation period. METHODS: Eighty-eight presbyopic subjects, across four clinical sites, wore each of four multifocal soft contact lenses (ACUVUE BIFOCAL, Focus Progressives, Proclear Multifocal, and SofLens Multifocal) for 4 days of daily wear. Comprehensive performance assessments were conducted at dispensing and after 4 days wear and included the following objective metrics: LogMAR acuity (contrast, 90% and 10%; illumination, 250 and 10 cd/m; distance, 6 m, 100 cm, and 40 cm), stereopsis (RANDOT), reading critical print size and maximum speed and range of clear vision at near. Subjective assessments were made, with 100-point numerical rating scales, of comfort, ghosting (distance, near), visual quality (distance, intermediate, and near), and the appearance of haloes. At two sites, subjects (n = 39) also rated visual fluctuation (distance, intermediate, and near), facial recognition, and overall satisfaction. RESULTS: Among the objective variables, significant differences (paired t test, P<0.05) between dispensing and 4 days were found only for range of clear vision at near (2.9 ± 2.0 cm; mean difference ± standard deviation) and high contrast near acuity in low illumination (-0.013 ± 0.011 LogMAR). With the exception of insertion comfort, all subjective variables showed significant decrements over the same period. Overall satisfaction declined by an average of 10.9 ± 5.1 points. CONCLUSIONS: Early assessment is relatively unrepresentative of performance later on during multifocal contact lens wear. Acuity based measures of vision remain substantially unchanged over the medium term, apparently because these metrics are insensitive indicators of performance compared with subjective alternatives. © 2009 Lippincott Williams & Wilkins.
Schulze,M. M., Hutchings,N., Simpson,T. L. The perceived bulbar redness of clinical grading scales. Optometry and Vision Science 2009;86,11:E1250-E1258. [ Show Abstract ]
Purpose. To use a psychophysical scaling method to estimate the perceived redness of reference images of the McMonnies and Chapman-Davies (six reference levels), Institute for Eye Research (four), Efron (five), and Validated Bulbar Redness (five) bulbar redness grading scales. Methods. Regions of interest were cropped out of the grading scale reference images; three separate image sets (color, grayscale, and binarized) were created for each scale, combining to a total of 20 images per image set. Ten naïve observers were asked to arrange printed copies of the 20 images per image set across a distance of 1.5 m on a flat surface, so that separation reflected their perception of bulbar redness; only start and end point of this range were indicated. The position of each image was averaged across observers to represent the perceived redness for this image, within the 0 to 100 range. Subjective data were compared with physical attributes (chromaticity and spatial metrics) of redness. Results. For each image set, perceived redness of the reference images within each scale was ordered as expected, but not all consecutive within-scale levels were rated as having different redness. Perceived redness of the reference images varied between scales, with different ranges of severity being covered by the images. Perception of redness severity depended on the image set (repeated-measures analysis of variance; all p ≤ 0.0002). The perceived redness was strongly associated with the physical attributes of the reference images. Conclusions. Subjective estimates of redness are based on a combination of chromaticity and vessel-based components. Psychophysical scaling of perceived redness lends itself to being used to cross-calibrate these four clinical scales. © 2009 American Academy of Optometry.
Sorbara,L., Jones,L., Williams-Lyn,D. Contact lens induced papillary conjunctivitis with silicone hydrogel lenses. Contact Lens and Anterior Eye 2009;32,2:93-96. [ Show Abstract ]
PURPOSE: To describe the refitting of a soft lens wearer into a silicone hydrogel lens due to neovascularization. This change, in turn, caused contact lens induced papillary conjunctivitis (CLPC) and a further refitting was necessary. METHODS: The patient was refit into a high Dk surface treated silicone hydrogel with a high modulus value. A second refitting was undertaken into a lower Dk silicone hydrogel contact lens with a lower modulus value which had no surface treatment but incorporated an internal wetting agent. RESULTS: A high Dk/t lens was used to resolve existing neovascularization and chronic hyperaemia. Subsequently, CLPC response occurred, possibly due to a combination of factors, resulting in irritation of the palpebral conjunctiva. This resulted in temporary lens discontinuation. A second silicone hydrogel lens was fit, along with the use of a non-preserved care system, which led to improvement and eventual resolution of the condition. CONCLUSION: High Dk silicone hydrogel lenses have shown excellent efficacy in resolving hypoxic complications such as neovascularization and hyperaemia. However, attention needs to be paid to their potential effect on the upper tarsal plate. More than one silicone hydrogel lens may be needed to help resolve these issues.
Sorbara,L., Peterson,R., Woods,C., Fonn,D. Multipurpose disinfecting solutions and their interactions with a silicone hydrogel lens. Eye and Contact Lens 2009;35,2:92-97. [ Show Abstract ]
PURPOSE:: To assess the compatibility of a new silicone hydrogel lens, asmofilcon A (with four multipurpose disinfecting solutions: OPTIFREE RepleniSH, ReNu MultiPlus, Solo-Care Aqua and MeniCare Soft). Ocular responses and subjective responses were monitored with each lens-care system combination. METHODS:: The study was conducted as a prospective, bilateral, clinical trial with a single-masked investigator, and randomized cross-over design with four phases, (one for each care system). Each study phase comprised of two consecutive days of lens wear where the lenses were inserted on day 1 directly from the blister-packs and worn for over 8 hr, then inserted on day 2 after overnight disinfection with one of the study lens care systems. Twenty-five adapted soft contact lens wearers who were able to wear their habitual lenses comfortably for more than 12 hr were recruited. RESULTS:: There were statistically significant differences in corneal staining found for all the lens-care systems when comparing the results of day 1 (from the blister pack) with day 2 (following care system use) (P < 0.05). ReNu MultiPlus solution had the highest grade for corneal staining at the 2-hr time point on day 2 which then decreased by 6 hr (P < 0.05). There was no difference between the lens care systems and the rating of subjective comfort over either of the two days. The rating of dryness and burning sensations were only slightly increased at 6 hr for all lens care systems except ReNu MultiPlus where burning was highest on insertion (P < 0.05). CONCLUSION:: Corneal staining observed in this study does not seem to have been related to the presence of polyhexamethylene biguanide (0.0001% wv) that was present in three of the four care systems. Only one care system (ReNu MultiPlus) demonstrated an associated level of corneal staining that was statistically significant; however, this was not considered to be of clinical relevance. These results suggest that using this novel surface-treated silicone hydrogel lens may result in less lens and lens care-related interactions. © 2009 Lippincott Williams & Wilkins.
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.
Varikooty,J., Simpson,T. L. The interblink interval I: The relationship between sensation intensity and tear film disruption. Investigative Ophthalmology and Visual Science 2009;50,3:1087-1092. [ Show Abstract ]
PURPOSE. To find the relationship between tear film drying and sensation during the interblink period. METHODS. One eye was taped shut, and after a blink the subjects were required to keep the other eye open. Digital video images of the ocular surface (with fluorescein) were obtained using a slit lamp biomicroscope while 23 subjects rated the intensity of the ocular surface sensation by adjusting a one-turn potentiometer to represent the strength of the sensation. They were trained to use the potentiometer before the data were collected. In addition, the characteristics of the sensation as spoken by the subject were recorded. RESULTS. The sensation was generally triphasic, with initial constant sensation and a subsequent biphasic period, with intensity increasing slowly followed by a rapid increase before the subjects blinked (correlations were all r > 0.95). Tear film drying dynamics were also biphasic, and drying and sensation were strongly associated, with a correlation of 0.94 between the break in the bilinear functions of sensation and drying. CONCLUSIONS. The method provides novel information about the development of ocular sensation during ocular surface drying. As evidenced by the complex functions required to adequately describe the relationships, tear film drying and ocular surface sensations are associated in complex ways. © Association for Research in Vision and Ophthalmology.
Woods,C. A., Cumming,B. The impact of test medium on use of visual analogue scales. Eye and Contact Lens 2009;35,1:6-10. [ Show Abstract ]
OBJECTIVES: Visual analog scales are frequently used as a means of allowing participants to rate symptoms during clinical trials. The accuracy and reproducibility of these scales play an important role in determining the experimental value of the data they provide. This study was initiated to compare the data collected using paper- and computer-based (Tablet PC) analog scales to better understand the variability in data provided by a visual analog scale. METHODS: Thirty participants rated ocular comfort, redness, and clarity of vision (right and left eyes) on a nondemarcated horizontal line on both paper and a Tablet PC. Measurements were taken in the morning between the hours of 8:30 and 10:30 am and again the same day between 2:30 and 4:30 pm. RESULTS: The mean difference between the measures recorded in the morning for the 2 media was 2.6 ± 0.9 (confidence intervals, 2 standard errors of the differences) units on a 100 unit scale, with the Tablet PC having the higher mean measure. The limits of agreement (2 standard deviations of the differences) was 9.4 units. Comparing the difference of the differences (1.0 ± 1.3) between the 2 methods of measure (morning vs. afternoon) the visual analog scales on the Tablet PC seemed to have good reproducibility of agreement in comparison with the paper version. CONCLUSIONS: Discrepancy analysis yielded no significant difference and slight bias between paper- and computer-based analog scales. Repeatability of measures using the Tablet PC was also demonstrated. These results suggest that the choice of medium does not significantly influence the outcome for subjective analog scales. © 2009 Lippincott Williams & Wilkins, Inc.
Woods,J., Woods,C. A., Fonn,D. Early symptomatic presbyopes-What correction modality works best?. Eye and Contact Lens 2009;35,5:221-226. [ Show Abstract ]
Purpose: To compare the performance of a low-addition silicone hydrogel multifocal soft lens with other soft lens correction options in a group of habitual soft lens wearers of distance correction who are symptomatic of early presbyopia. METHOD: This clinical study was designed as a prospective, double-masked, randomized, crossover, dispensing trial consisting of four 1-week phases, one for each of the correction modalities: a low-addition silicone hydrogel multifocal soft lens, monovision, habitual correction, and optimized distance visual correction. The prescriptions of all modalities were finalized at a single fitting visit, and the lenses were worn according to a randomized schedule. All lenses were made from lotrafilcon B material. A series of objective vision tests were conducted: high- and low-contrast LogMAR under high- and low-room lighting conditions, stereopsis, and critical print size. A number of other data collection methods used were novel: some data were collected under controlled laboratory-based conditions and others under "real-world" conditions, some of which were completed on a BlackBerry hand-held communication device. RESULTS: All participants were able to be fit with all four correction modalities. Objective vision tests showed no statistical difference between the lens modalities except in the case of low-contrast near LogMAR acuity under low-lighting levels where monovision (+0.29 ± 0.10) performed better than the multifocal (+0.33 ± 0.11, P=0.027) and the habitual (+0.37 ± 0.12, P<0.001) modalities. Subjective ratings indicated a statistically better performance provided by the multifocal correction compared with monovision, particularly for the vision associated with driving tasks such as driving during the daytime (93.3 ± 8.8 vs. 84.2 ± 23.7, P=0.05), at nighttime (88.8 ± 11.7 vs. 74.9 ± 23.6, P=0.001), any associated haloes or glare (92.0 ± 10.6 vs. 78.0 ± 22.8, P=0.003), and observing road signs (90.1 ± 11.8 vs. 79.4 ± 20.2, P=0.027). Preference for the multifocal compared with monovision was also reported when watching television (95.0 ± 6.4 vs. 82.6 ± 20.1, P=0.001) and when changing focus from distance to near (87.0 ± 13.4 vs. 66.1 ± 32.2, P<0.001). CONCLUSIONS: For this group of early presbyopes, the AIR OPTIX AQUA MULTIFOCAL-Low Add provided a successful option for visual correction, which was supported by the results of subjective ratings, many of which were made during or immediately after performing such activities as reading, using a computer, watching television, and driving. These results suggest that making a prediction of "success or not" based on consulting room acuity tests alone is probably unwise. Copyright © Contact Lens Association of Ophthalmologists, Inc.
Young,G., Keir,N., Hunt,C., Woods,C. A. Clinical evaluation of long-term users of two contact lens care preservative systems. Eye and Contact Lens 2009;35,2:50-58. [ Show Abstract ]
PURPOSE: To clinically evaluate long-term users of two different contact lens care preservative systems and to investigate whether prolonged use is associated with an increase in the prevalence of dry eye. METHODS: Eighty-nine wearers of group IV hydrogel or silicone hydrogel lenses participated in this one-visit, investigator-masked study. Subjects were required to have consistently used a polyhexamethylene biguanide (PHMB) or polyquaternium-1 (PQT) based solution for 2 years. Consistent use was defined as 80% for the past 2 years and 100% for the past year. Clinical assessments included: average and comfortable wear time; overall and end-of-day comfort; signs of dryness, discomfort, burning or stinging, grittiness or scratchiness and visual changes; non-invasive and fluorescein break-up-time; pre-ocular tear film lipids, tear meniscus height, Schirmer and fluorescein clearance tests; limbal and bulbar hyperemia; palpebral roughness; corneal and conjunctival staining; lens front surface wetting; and lens film deposits. RESULTS: Significantly more grittiness or scratchiness was reported by subjects using a PHMB-containing system (67% vs. 44%; P = 0.02). Palpebral roughness and hyperemia were significantly greater in the PHMB group wearing group IV lenses (P = 0.01 and P = 0.05, respectively). Corneal staining was significantly higher in the PHMB users in all four peripheral sectors (P < 0.01). Nasal and temporal conjunctival staining was also significantly higher for users of PHMB-containing systems (P < 0.05). Front surface lens wettability was significantly better for group IV PQT users compared to PHMB users (P = 0.008), with 84% vs. 72%, respectively, with lenses graded by the investigator as having "good" or "excellent" wettability. Significantly higher levels of lens front surface film deposits were noted with PHMB users (P = 0.007), with 58% of group IV lenses treated with PHMB compared with 38% of group IV lenses treated with PQT showing some lens front surface film deposition. No significant differences between the two preservative system groups were noted for the range of dry eye evaluations nor the remaining clinical assessments. CONCLUSIONS: Differences in both ocular and lens characteristic were observed between long-term users of two preservative systems used in many contact lens multi-purpose solutions. The findings from this study did not support the hypothesis that prolonged use of PHMB-containing solutions leads to dry eye. Additional studies including a larger sample size and perhaps longer use of the systems could help to further elucidate differences in clinical performance between systems.