Peer-reviewed Articles

Please use the archived list on the right to look at past peer-reviewed articles.

2005

Chalmers,R. L., Begley,C. G., Edrington,T., Caffery,B., Nelson,D., Snyder,C., Simpson,T. The agreement between self-assessment and clinician assessment of dry eye severity. Cornea 2005;24,7:804-810. [ Show Abstract ]

Purpose: The purpose of this analysis was to measure the degree of agreement between clinicians' assessment and subjects' self-assessment of dry eye severity in a cross-sectional, observational dry eye study. A secondary purpose was to identify the role of gender and age in that concordance. Methods: In a cross-sectional observational study, 162 dry eye subjects and 48 controls were recruited from clinical databases of ICD-9 codes in 6 clinical sites. Before examination, subjects gave a global self-assessment of the severity of their dry eye from "none" to "extremely severe." After a clinical examination that included dry eye tests, the clinician discussed the subjects' symptoms and then gave global clinician assessment of dry eye from "none" to "severe." We measured the degree of agreement in these global measures. Results: Although the correlation and agreement between clinician and self-assessment was significant (r = 0.720, P = 0.000; weighted K = 0.471; 95% CI = 0.395, 0.548; P = 0.000), the clinician assessment underestimated the severity in 40.9% of the subjects by at least 1 grade compared with the subjects' self-assessment. Over 54% of subjects over age 65 and 43% of the female subjects had their condition underestimated by the clinician (P < 0.05). Conclusions: Clinicians often relatively underestimated the severity of the subjects' self-assessment of dry eye in this clinical study, especially among the elderly and women. Eye care practitioners need better, more quantitative tools for the assessment of ocular surface symptoms to improve the concordance in severity assessment and to meet the needs of this symptomatic patient population by offering them appropriate treatments. Copyright © 2005 by Lippincott Williams & Wilkins.

Feng,Y., Simpson,T. L. Comparison of human central cornea and limbus in vivo using optical coherence tomography. Optometry and Vision Science 2005;82,5:416-419. [ Show Abstract ]

Purpose. The purpose of this study was to compare central corneal and limbal total and epithelial thickness using a commercially available optical coherence tomographer. Methods. A Humphrey-Zeiss Optical Coherence Tomographer (OCT [Carl Zeiss, Meditec, Dublin, CA]) was used to obtain corneal images from 10 subjects. Central corneal and limbal total and epithelial thickness of both eyes were measured using the OCT. Each OCT image comprised 100 measurements, 10 nasal, 10 central, and 10 temporal measurements from each image were analysed. Results. The central corneal and epithelial thickness of the right and the left eyes were 507.9 ± 35.8 μm, 58.4 ± 2.5 μm, 506.9 ± 37.4 μm, and 58.5 ± 2.5 μm, respectively. There were no differences between eyes (p > 0.05). The nasal and temporal limbal total and epithelial thickness of the right and left eyes were 703.8 ± 32.1 μm, 704.9 ± 31.0 μm, 76.8 ± 3.5 μm, 77.9 ± 2.9 μm, 704.4 ± 31.8 μm, 706.3 ± 32.5 μm, 77.5 ± 2.8 μm, and 77.8 ± 2.5 μm, respectively. There were no differences between the nasal and temporal total and epithelial thickness of both eyes (p > 0.05). However, there was a statistical difference between the central corneal and limbal total and epithelial thickness (both p < 0.05). Conclusions. Central cornea and limbus are measurably different using OCT. Central cornea is thinner than limbus for both total thickness and epithelial thickness. There is no difference between eyes of central corneal and limbal total and epithelial thickness. Optical Coherence Tomography is a useful instrument for in vivo human limbal morphometry. Copyright © 2005 American Academy of Optometry.

Feng,Y., Simpson,T. L. The inhibitory interaction between human corneal and conjunctival sensory channels. Investigative Ophthalmology and Visual Science 2005;46,4:1251-1255. [ Show Abstract ]

PURPOSE. To explore human corneal and conjunctival sensory channels at suprathreshold level. METHODS. Ten healthy human subjects participated in the study. The Belmonte pneumatic esthesiometer was used to apply mechanical and chemical stimuli to the central cornea and temporal conjunctiva of the left eye. Stimuli were applied in a paired and unpaired way for conjunctival stimulation. A 100-point visual analog scale (VAS) was used to rate the intensity of the stimulus. RESULTS. The magnitudes of the sensation evoked from the conjunctiva were different when using different methods for presenting stimuli to the ocular surface. When stimuli were applied to the conjunctiva alone, the magnitude of the sensation was stronger than when the stimuli were applied in pairs to the cornea and conjunctiva for both mechanical (P = 0.04) and chemical (P = 0.02) stimulation. CONCLUSIONS. The relatively strong discomfort evoked from the cornea appears to suppress partially the relatively weaker conjunctival stimulation. This manifested as the conjunctival sensory transducer function being shallower (less intense sensation) when immediately preceded by corneal stimulation than when the conjunctival sensory transducer functions were measured alone (unpaired). The underlying mechanism could be adaptation or some other inhibitory effect, such as diffuse noxious inhibitory control. At some level therefore, corneal and conjunctival sensory channels are not independent. Copyright © Association for Research in Vision and Ophthalmology.

Fonn,D., Bruce,A. S. A review of the Holden-Mertz criteria for critical oxygen transmission. Eye and Contact Lens 2005;31,6:247-251. [ Show Abstract ]

Purpose. Holden and Mertz established the foundations for the new generation of silicone hydrogel contact lenses for daily and extended wear in 1984. Absence of lens-induced corneal swelling was their premise and although this was possible with daily wear, the goal with extended wear seemed almost impossible because of the limitation of hydrogel materials. Experience with extended and daily wear of disposable contact lenses during the last 2 decades and, more recently, with silicone hydrogels has led to the reconsideration of the validity of the findings of Holden and Mertz. Results. A pivotal influence on the Holden and Mertz critical Dk/t value for closed-eye lens wear was exerted by two numbers: the no-lens wear corneal edema level (4%) and the silicone lens data point (Dk/t of 182 × 10-9, closed-eye edema level of 2.6%). Subsequent publications appear to give a more accurate assessment of the no-lens closed-eye corneal edema level, and there are also more recent measurements of silicone hydrogel lens Dk/t and corneal edema responses. Conclusions. It now appears that the Holden and Mertz criteria for extended-wear critical Dk/t should be revised upwards to at least 125 × 10 -9. © 2005 Contact Lens Association of Ophthalmologists, Inc.

Fonn,D., Sweeney,D., Holden,B. A., Cavanagh,D. Corneal oxygen deficiency. Eye and Contact Lens 2005;31,1:23-27. [ Show Abstract ]

Objectives. To compare the ocular effects of low Dk hydrogel and high Dk silicone hydrogel contact lenses. Methods. A review of recent literature was conducted to determine the effects of wearing low and high Dk soft lenses on corneal swelling, vascular response, refractive error and the corneal epithelium. Results. High Dk silicone hydrogel contact lenses became available for research and clinical practice almost 10 and 5 years ago respectively. During that time many studies have been conducted and it has been demonstrated repeatedly how much improvement there has been to the physiological response of the eye particularly when wearing the lenses on an overnight basis. Conclusions. Although silicone hydrogels only constitute about 2% of current wearers, their positive effects on the eye compared with low Dk hydrogel lenses should make them the most dominant lenses in the near future. © 2005 Contact Lens Association of Ophthalmologists, Inc.

Henderson,L., Bond,D., Simpson,T. The association between eye color and corneal sensitivity measured using a Belmonte esthesiometer. Optometry and Vision Science 2005;82,7:629-632. [ Show Abstract ]

Purpose. The purpose of this study is to determine the association between corneal sensitivity measured using a pneumatic esthesiometer and eye color quantified objectively. Methods. Twenty subjects had ocular surface sensitivity measured using a Belmonte esthesiometer. An ascending method of limits followed by the method of constant stimuli were used to estimate 1) cold detection thresholds, 2) discomfort detection thresholds (both using pneumatic stimuli at 20°C, 3) mechanical detection thresholds using pneumatic stimuli at 50°C (ocular surface temperature approximately 33°C), and 4) percent CO2 chemical detection thresholds using 50°C pneumatic stimuli at flow rates set at half of each subject's pneumatic detection threshold (therefore detected by the chemical content and not the mechanical content). Eye color was estimated 1) clinically by two observers ranking the color (light to dark) of digital images of each subject's iris, 2) photometrically by measuring iris luminance, and 3) using chromaticity obtained from a Photo Research 650 spectroradiometer with controlled illumination. Correlation and linear and nonlinear regression analyses were used to examine relationships between variables. Results. There were no associations between eye color (determined clinically or objectively) for mechanical and chemical detection thresholds (best r2 = 0.15, all p > 0.05). There was a significant linear association between 20° detection thresholds and eye color (r2 = 0.39), which was substantially improved with a two-line function (part level and part increasing linearly, r2 = 0.65). Conclusions. We were generally unable to demonstrate the relationship between eye color and sensitivity reported previously using a Cochet-Bonnet esthesiometer. However, for a subset of subjects with palest irises, there appears to be a linear association between eye color and sensitivity to cooling stimuli. Copyright © 2005 American Academy of Optometry.

Mertzanis,P., Abetz,L., Rajagopalan,K., Espindle,D., Chalmers,R., Snyder,C., Caffery,B., Edrington,T., Simpson,T., Nelson,J. D., Begley,C. The relative burden of dry eye in patients' lives: Comparisons to a U.S. normative sample. Investigative Ophthalmology and Visual Science 2005;46,1:46-50. [ Show Abstract ]

PURPOSE. To assess the relative burden of dry eye in daily life by comparing Short Form-36 (SF-36) responses from individuals with and without dry eye against U.S. norms. METHODS. Assessment of 210 people, 130 with non-Sjögren's keratoconjunctivitis sicca (non-SS KCS), 32 with Sjögren's Syndrome (SS), and 48 control subjects. The study population data and published normative SF-36 data were compared. Dry eye severity was assessed by recruited severity (control, non-SS KCS, SS), patient self-report (none, very mild/mild, moderate, severe/extremely severe), and clinician-report (none, mild, moderate, severe). Age- and gender-matched norms were compared with all defined severity groups. RESULTS. Compared with the norms, control subjects scored higher on all SF-36 scales. Effect size (ES) ranged from 0.15 to 0.52. Non-SS KCS patients had lower Role-Physical (ES = -0.07), Bodily Pain (ES = -0.08), and Vitality (ES = -0.11) scores, indicating more dry eye impact on those areas versus the norm. All SF-36 scale scores except Mental Health (ES = 0.12) were lower in the SS group than the adjusted norm (ES range: -0.16 to -0.99). Regardless of severity classification, mild patients consistently had lower Role-Physical and Bodily Pain scores than the norm, suggesting impact on daily roles (ES < 0.2). Patients with moderately severe disease also experienced less vitality and poorer general health. The group with severe disease scored lower than the norm across all domains (ES range: -0.14 to -0.91) except Role-Emotional (ES = 0.13) and Mental Health (ES = 0.23). CONCLUSIONS. These results indicate dry eye's negative impact on everyday life, particularly in daily activities. Further research using disease-specific measures to examine dry eye's impact is underway.

Sorbara,L., Fonn,D., Simpson,T., Lu,F., Kort,R. Reduction of myopia from corneal refractive therapy. Optometry and Vision Science 2005;82,6:512-518. [ Show Abstract ]

Purpose. The purpose of the study was to monitor the efficacy of corneal refractive therapy (CRT) lenses to reduce myopia over a 4-week period. Refractive error, keratometry, high and low contrast acuity, and subjective vision after 28 days of using CRT contact lenses were measured. Methods. Twenty-three myopes wore CRT HDS lenses, Dk = 100. The Nikon autokefractor/keratometer was used to measure the refractive error and keratometric changes. Visual acuity was measured using computerized high and low contrast charts and the subjects completed visual analog scales characterizing their vision on a daily basis. Measurements were performed at baseline (before lens insertion before sleep), immediately after lens removal the next morning and at 1, 3, 7, and 14 hours after eye opening. Measurements were made on the days following 1, 4, 10, and 28 nights of lens wear. After 72 hours of no lens wear, these parameters were again measured to assess corneal recovery. Results. The pretreatment manifest refraction (mean of OD and OS ± standard deviation [SD]) was -2.72 DS ± 1.06 and -0.55 DC ± 0.40. Myopic spherical equivalent refractive error (± SD) decreased by 1.30 DS ± 0.53 (range 0-3 D) immediately after lens removal on day 1 and by 2.59 DS ± 0.77 by day 28 (range 1.25-3.88 D). The cylinder remained unchanged. Uncorrected visual acuity improved by 5 lines after one night and reached 0.00 LogMAR (6/6) by day 4. Visual acuity was maintained throughout the day by day 10. The day and time effect of the spherical equivalent change and the central corneal radius of curvature were statistically significant (p < 0.01) up to day 10 and remained the same until day 28. Central (autokeratometer) Ks flattened by 1.28 D ± 1.35 after one night and 2.33 D ± 1.30 by day 28. The subjective vision improved significantly from day 1 to day 28 (p < 0.01) and was maintained throughout the day from day 4 to day 28 (p < 0.01). All measures did not recover completely to baseline after 72 hours of no lens wear. Conclusions. CRT lenses significantly reduced myopia, improved visual acuity and subjective vision, and flattened central corneal curvature. Maximal effect was achieved after 10 days and was maintained for the rest of the study period. Copyright © 2005 American Academy of Optometry.

Srinivasan,S., Joyce,E., Jones,L. W., Senchyna,M. Subconjunctival cyst-like formations following impression cytology. Contact Lens and Anterior Eye 2005;28,4:181-184. [ Show Abstract ]

Purpose: To report a case of an unusual adverse event subsequent to undertaking Conjunctival Impression Cytology (CIC). Methods: CIC was un dertaken on a 54-year-old healthy Caucasian female, using a 10 mm Millipore™ membrane on the bulbar conjunctiva. Prior to the CIC procedure, two drops of topical proparacaine (Alcaine®) were instilled and following the procedure two drops of artificial tears (GenTeal®) were administered. Results: The subject reported excessive bulbar conjunctival hyperaemia in the left eye 5 min postprocedure, with no marked pain or discomfort. Slitlamp biomicroscopic evaluation revealed several "bubbles" or cystic formations trapped underneath the conjunctival tissue, in association with moderate to severe bulbar conjunctival redness. These cysts began to regress fairly rapidly and completely disappeared within 1 h. Conclusion: CIC is a useful tool for studying the ocular surface; however, care should be taken while performing this mildly invasive procedure. This is the first report of bubble formation in the conjunctiva following CIC. Subjects should be advised about the short term redness and discomfort that could occur following CIC. © 2005 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

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.

Walline,J. J., Holden,B. A., Bullimore,M. A., Rah,M. J., Asbell,P. A., Barr,J. T., Caroline,P. J., Cavanagh,H. D., Despotidis,N., Desmond,F., Koffler,B. H., Reeder,K., Swarbrick,H. A., Wohl,L. G. The current state of corneal reshaping. Eye and Contact Lens 2005;31,5:209-214. [ Show Abstract ]

Purpose. The application of contact lenses to alter the shape of the cornea and temporarily reduce or eliminate myopia is known as orthokeratology, corneal refractive therapy, or corneal reshaping. It was first introduced in the 1960s, but high oxygen permeable materials and more sophisticated designs allow patients to wear contact lenses only during sleep, while dramatically improving the predictability and rate of myopia reduction. Many studies have shown that most corneal reshaping patients achieve uncorrected visual acuity of 20/25 or better that lasts all day long in one to two weeks of nighttime wear. 1-3 Treatment is primarily effective through central epithelial thinning and midperipheral epithelial and stromal thickening. Much remains to be learned about corneal reshaping contact lenses and their effects on the cornea. Methods. The authors reviewed existing knowledge and determined what needs to be learned in order to provide patients with appropriate informed consent prior to corneal reshaping contact lens wear. Results. While corneal reshaping contact lenses are effective at temporarily reducing or eliminating myopia, claims about the progress of myopia being controlled with corneal reshaping contact lenses should not be made until further studies are published in peer-reviewed literature. The incidence and prevalence of microbial keratitis related to corneal reshaping contact lens wear is not known. Any overnight wear of contact lenses increases the risk of infection, but it is not known whether the risks of microbial keratitis are greater for corneal reshaping overnight contact lens wearers than other form of overnight contact lens wear. It is also not known whether the risk of microbial keratitis is greater for children than adults, but we must determine if children are at greater risk than adults because many children are wearing corneal reshaping contact lenses. Conclusions. Finally, it is recommended that ongoing education be provided to practitioners and staff regarding safety, informed consent, and prevention of potential problems, with special emphasis on the critical need to properly and thoroughly disinfect lenses that will be worn overnight. © 2005 Contact Lens Association of Ophthalmologists, Inc.

Woods,C. A. Working better with GPs: Lessons to be learned from a study of health care networks in the management of diabetes. Clinical and Experimental Optometry 2005;891-2.