Tear plasmin activity with contact lens wear

Letters to the Editor

Convenience and safety are major motivating factors in the choice of a mode of correction for refractive errors. Extended wear of contact lenses is associated with greater convenience than daily wear, but questions remain concerning the safety and risks associated with this modality. This paper investigates the hurdles that have rendered extended wear an unfavorable option thus far and seeks to identify strategies to overcome these obstacles. We review the history of extended contact lens wear, focusing on soft extended wear for cosmetic use. Results of incidence and relative risk studies for the major complications are scrutinized. The factors that are associated with increased risk together with mechanisms which have been proposed on based on scientific research are analyzed to derive strategies for preventing adverse reactions in extended wear. Infectious keratitis associated with extended wear of contact lenses has been identified by the community as a major issue, although the degree of concern may be disproportionate. Current perceptions of the relative risk of extended wear versus daily wear in the context of the risk for nonwearers may be misplaced, and the role of eye closure versus consistency and duration of wear remains open to debate. In the minds of practitioners and patients, other adverse reactions may be of greater significance in rejecting extended wear. Nonetheless, the potential extent of injury from infection demands attention. Studies collectively attest that corneal hypoxia during extended wear is a potential causative mechanism in infectious keratitis, suggesting that the provision of higher oxygen levels to the cornea will reduce morbidity rates from this unwanted complication. However, the issues of stagnation of the post-lens tear film during eye closure, mechanical properties of the lens, and lens movement remain unresolved and may prove to be contributing factors to adverse responses. Attention to oxygen permeability and mechanical properties of soft contact lenses should solve the remaining problems with extended wear. Materials currently under development promise to meet at least some of the desired properties and may lead to the long-awaited advent of safe extended wear.

To demonstrate that corneal light-backscatter can be measured objectively during corneal swelling by optical coherence tomography (OCT). One eye (randomly selected) of 20 non-contact-lens wearers (10 men and 10 women; mean age, 35.6 +/- 9.6 years) was patched during 3 hours of soft contact lens (SCL) wear. The contralateral eye acted as the control. Central corneal images were captured before and after SCL wear at 20-minute intervals over 100 minutes using optical coherence tomography (OCT) to obtain corneal thickness and light-backscatter profiles. OCT backscattered light of the epithelial layer (decided by the thickness measurements) and 10 equally divided layers of the remaining cornea were analyzed with a custom software program. Two baseline measurements were taken at different visits before lens wear to test the repeatability of light-backscatter measurements. From two baseline measurements, repeated measurements showed good repeatability of normalized backscatter results. Immediately after contact lens removal, total central corneal thickness increased significantly by 13.8% +/- 2.3% (mean +/- SD) compared with baseline (P = 0.0001, paired t-test) and then decreased during the deswelling course. Corneal backscattered light changed significantly (repeated-measures ANOVA [Re-ANOVA]: F((50, 950)) = 2.22, P = 0.0001) after lens wear, and a significant increase in backscatter was found in the epithelial layer (36.4%) and the most posterior corneal layer (35.6%) immediately after lens removal (post hoc test, P = 0.005). There was a strong correlation (r = 0.9375, P < 0.05) between the change in backscatter and corneal swelling during the deswelling period. The backscatter recovery rate was approximately the same for both epithelial and posterior layers after lens removal. Light-backscattering analysis with OCT seems to be a promising and repeatable method of objectively measuring corneal backscatter. This study has demonstrated that corneal backscattered light increased in the anterior and posterior layers of the cornea during corneal swelling induced by contact lens wear and eye closure.

A case-control study of ulcerative keratitis in soft contact lens (CL) users compared three groups of daily wear or extended wear patients: (a) 86 patients with ulcerative keratitis, (b) 61 hospital-based controls, and (c) 410 population-based controls. Overnight lens use, whether regularly with extended wear lenses or occasionally with daily wear lenses, emerged as the preeminent risk factor for ulcerative keratitis. It increased risk by 10 to 15 times in users of extended wear lenses and by 9 times in users of daily wear lenses when these groups were compared with subjects engaged in strict daily wear of daily wear lenses. Even when actual overnight wear was not taken into account, the relative risk was four times greater in users of extended wear lenses than in users of daily wear lenses. The study found a marginal association (p = 0.056) between lens care frequency in general and ulcerative keratitis in comparing ulcerative keratitis cases with population controls. Of the individual hygiene-related measures, evidence of a protective effect was strongest for cleaning the lens case. Smokers showed a threefold greater risk than nonsmokers, regardless of the type of lens worn. An incidence study found the rate of ulcerative keratitis to be approximately 1 in 2,500 daily wear lens users and 1 in 500 extended wear lens users per year. This finding was statistically consistent with the risk ratio noted in the case-control study. Extrapolations suggest that 4,000 of the 9 million U.S. users of daily wear soft lenses develop ulcerative keratitis annually. Among the 4 million U.S. extended wear soft lens users, 8,000 may do so per year.

Purpose: To investigate the effect of contact lens (CL) wear on ocular surface sensitivity and to determine and summarise the relationship between corneal sensitivity and CL comfort. Material and Methods: A literature search was carried out in PubMed, Scopus and Google Scholar, whereby relevant publications were reviewed and summarised during the period of 13th and 20th November 2023. Results: For the evaluation of the published literature, it is important to acknowledge that corneal sensitivity measurements are influenced by both, the psychophysical technique and the type of instrument used. Study results show a clear but reversible decrease in corneal sensitivity with oxygen-­impermeable polymethyl methacrylate (PMMA) contact lens wear, but little or no effect during daily rigid gas permeable (RGP) CL wear. The results for soft CL wear are more complicated: A decrease in corneal sensitivity may be observed during daily wear of hydrogel CLs with low oxygen permeability, however no change or only a small decrease (depending on the applied measurement method) during silicone hydrogel CL wear. Some studies even found a slight sensitisation with this CL material. Conclusion: Based on the published study results, it is reasonable to assume that hypoxia is the most likely cause of the reduction in corneal sensitivity during daily CL wear. Successful CL wear with materials that have a sufficiently high oxygen transmissibility has a negligible effect on corneal sensitivity. However, an increased sensation of irritation, particularly with symptomatic CL wear may be observed. This could be caused by (subclinical) inflammatory reactions.

This evaluation was conducted as part of a protocol entitled Evaluation of the Menicon Z Rigid Gas Permeable Contact Lens for up to 30 Days Extended Wear. The purpose of the protocol was to compare corneal endothelial morphology changes after wearing rigid gas-permeable (RGP) Menicon Z contact lenses, continuously for up to 30 days, with ACUVUE (Johnson & Johnson Vision Care) hydrogel contact lenses, worn for up to 6 nights of extended wear. Sixty patients, who were adapted to RGP daily wear and soft contact lens daily wear, were recruited at two study sites. The thirty subjects who wore RGP daily wear lenses were fitted with the Menicon Z (tisilfocon A, oxygen permeablility [Dk] = 163) RGP contact lens comprised the test group. The control group subjects (n = 30 former users of daily wear soft contact lenses) were fitted with ACUVUE (etafilcon A, Dk = 28) hydrogel contact lenses. After a 2-week adaptation period of daily wear, subjects began extended wear. Endothelial imaging was performed at the two study sites in this multicenter study (University Hospitals of Cleveland/Case Western Reserve University Department of Ophthalmology [CWRU] and The Ohio State University [OSU]). The hydrogel lens group was instructed to wear their lenses for 7 days and 6 nights before discarding the lenses and to sleep with no lenses on the seventh night. The RGP group was permitted to wear the lenses for up to 30 days and 29 consecutive nights before removing the lenses for cleaning and overnight soaking. CWRU had 24 patients (12 soft contact lens and 12 rigid contact lens) and OSU had 21 patients (12 soft contact lens and 9 rigid contact lens) who completed the study and were included in the analyses. Patients who were withdrawn from the study at CWRU included one RGP patient dropped out because of pregnancy; one RGP patient developed vascularized limbal keratitis and discomfort; one could not be fitted with a bitoric RGP; two soft lens patients moved from the area, and one dropped out because of dry eyes. At OSU, four patients dropped out due to discomfort (two in each lens type);one moved from the study area; one decided not to participate soon after the consent visit; one had worries of reduced vision at 6 months; one subject's attitude changed prior to the 6 month visit; and one subject was withdrawn for reasons of poor study schedule compliance. The Menicon Z lens wearers in this study did not show significant endothelial cell morphology changes after 1 year of nearly continuous contact lens wear. This finding is particularly important considering the RGP wearers in this study were older by a average of 10 years (mean age approximately 40) and had worn their contact lenses an average of almost 10 years longer than the soft contact lens wearers.

Complement activation fragments have been detected in the anterior segment during 1) eye closure, 2) contact lens wear, and 3) in some contact lens-associated pathologies. The decay-accelerating factor (DAF), a membrane-associated complement regulatory protein that inhibits the central C3 amplification convertases of the cascade, is present on both the ocular surface and in tears. In this study, we measured levels of tear DAF in asymptomatic contact lens patients and in patients who presented with contact lens-associated complications. Tears were collected from 55 patients using capillary pipettes. Subjects included normal non-contact lens wearing controls (N = 14), asymptomatic soft (N = 13) and rigid gas permeable (N = 5) wearers, and individuals with contact lens-induced acute red eye (CLARE) (N = 4), ulcerative keratitis (N = 3), giant papillary conjunctivitis (GPC) (N = 8), contact lens peripheral ulcers (N = 3), and infiltrative keratitis (N = 5). Levels of DAF were assessed using a two-site immunoradiometric assay using anti-DAF monoclonal antibodies. The mean concentration of DAF in normal controls was found to be 149+/-78 ng/ml, 117+/-59 ng/ml, and 111+/-86 ng/ml for noncontact lens patients, and asymptomatic soft and rigid gas permeable lens wearers, respectively. In the conditions of CLARE, infiltrative keratitis, and GPC, DAF concentrations were significantly reduced compared with normal noncontact lens controls. Compared with asymptomatic soft lens patients, the condition of infiltrative keratitis showed a significant reduction in tear DAF. This study documents a trend toward decreased levels of tear DAF in patients with the contact lens associated inflammatory conditions CLARE, GPC, and infiltrative keratitis. Tears of patients with infiltrates show the most significant reduction of tear DAF. The reductions may be associated with enhanced complement activation contributing to the pathogeneses of infiltrative keratitis and associated ocular surface diseases.

Contact Lens Wear Is Associated with Decrease of Meibomian Glands

This paper discusses contact lenses in a military environment and reports the results of a literature survey, an extensive questionnaire sent to 1400 spectacle and contact lens wearers, and a short questionnaire given to soldiers taking part in a large scale and long military maneuver. Only a small number of publications were found concerning the relation between adverse environmental conditions and contact lens wearing. In Vietnam dust and poor hygiene often led to eye irritations that precluded the wearing of contact lenses by soldiers. Nevertheless, persons in the army are often in favor of contact lenses. In the air force and navy, wearing contact lenses seems compatible with nearly all military duties. A questionnaire was sent to all known contact lens wearers in the Dutch army and air force and to about an equal number of spectacle wearers. The responses indicate that the proportion of contact lens wearers is 1.8%. The distribution of hard vs. soft lenses was 60 and 40%, respectively. Military personnel wore their lenses during nearly all daily activities. Most contact lens wearers were of the opinion that in military conditions contact lenses have advantages over spectacles. To obtain more information on field exercises, a second questionnaire was handed out immediately after a large-scale NATO field maneuver. Twenty percent of the contact lens wearers had decided in advance not to wear their lenses, but another 30% ceased wearing their lenses during the exercise. It was recommended that for nearly all functions and/or conditions, wearing of contact lenses should be allowed, but that during extended field exercises wearing of hard contact lenses should be discouraged.

This paper discusses contact lenses in a military environment and reports the results of (1) a literature survey, (2) an extensive questionnaire sent to 1400 spectacle and contact lens wearers, and (3) a short questionnaire given to soldiers taking part in a large scale and long military maneuver. Only a small number of publications were found concerning the relation between adverse environmental conditions and contact lens wearing. In Vietnam dust and poor hygiene often led to eye irritations that precluded the wearing of contact lenses by soldiers. Nevertheless, persons in the army are often in favor of contact lenses. In the air force and navy, wearing contact lenses seems compatible with nearly all military duties. A questionnaire was sent to all known contact lens wearers in the Dutch army and air force and to about an equal number of spectacle wearers. The responses indicate that the proportion of contact lens wearers is 1.8%. The distribution of hard vs. soft lenses was 60 and 40%, respectively. Military personnel wore their lenses during nearly all daily activities. Most contact lens wearers were of the opinion that in military conditions contact lenses have advantages over spectacles. To obtain more information on field exercises, a second questionnaire was handed out immediately after a large‐scale NATO field maneuver. Twenty percent of the contact lens wearers had decided in advance not to wear their lenses, but another 30% ceased wearing their lenses during the exercise. It was recommended that for nearly all functions and/or conditions, wearing of contact lenses should be allowed, but that during extended field exercises wearing of hard contact lenses should be discouraged.

Several investigators have reported that significant corneal edema develops when daily wear hydrogel lenses are worn with the eyes closed. The amount of edema that develops when extended wear hydrogel lenses are worn with eye closure is not well documented. This study compared the amount of corneal edema that developed when subjects wore one daily wear lens with the edema that developed when they wore three lens types designed for extended wear. The daily wear lens was the U3 series Bausch &amp; Lomb Soflens contact lens. The extended wear lenses were the Cooper Permalens, the Soft Lens Hydrocurve II 55 lens, and the Sauflon PW lens. The five subjects developed only small amounts of corneal edema when they wore the four lens types under opened‐eye conditions but they developed significant amounts of corneal edema when they wore the four lens types for 3‐hr periods with eye closure. The amount of corneal edema correlated well with the oxygen transmissibility (DK/ L) of the study lenses. The results can be used to predict the amount of corneal edema that the average patient will develop initially when wearing a hydrogel lens of known water content or oxygen permeability (DK) and thickness (L) under opened and closed‐eye conditions.

To evaluate the recurrence rates of herpes simplex virus (HSV) keratitis in contact lens wearers compared with non-contact lens wearers. Retrospective cohort study. Charts of patients diagnosed with HSV keratitis seen at the Cleveland Clinic between January 2001 and December 2004 were reviewed. One hundred seventeen patients were included in this study: 21 contact lens wearers and 96 non-contact lens wearers. Contact lens wearers were found to have a higher median recurrence rate (0.4 episodes/year) compared with non-contact lens wearers (0.2 episodes/year) (P=0.02). A multivariate regression evaluating factors predictive of the number of recurrences found that contact lens use remained a significant predictive variable (P=0.02) when accounting for patient demographic and disease factors and variable follow-up time. Patients with a history of HSV keratitis should be counseled about the potential increased risk of recurrence that may be associated with contact lens wear.

Childhood and lifetime risk comparison of myopia control with contact lenses

Background: The aim of this study was to monitor changes in keratocyte density during extended contact lens wear and to explore the possible role of hypoxia and oedema in any changes observed. Methods: Twenty‐three neophyte myopic subjects wore a high Dk/t lens (Pure Vision) in one eye and a low Dk/t lens (Acuvue 2) in the other eye on an extended wear basis for six months. Slit‐scanning confocal microscopy and ultrasonic pachometry were performed on both eyes at baseline (before lens wear), after three and six months of lens wear, and one week after cessation of lens wear (the ‘post‐cessation’ visit). Results: No differences were established between die two lenses or between the three study visits for anterior stromal keratocyte density (KD). Posterior stromal KD was similar for the two lenses throughout the study. However, there was an overall drop in posterior KD of 14 per cent in bodl eyes at the six‐month visit, compared to die initial visit. Posterior KD at die six‐mondi visit was no different from diat at die post‐cessation visit. Corneal thickness was similar for die two lenses at die initial and post‐cessation visits, but was diree per cent greater for the eye wearing die Acuvue 2 lens at die six‐month visit. Conclusion: Extended contact lens wear causes a loss of keratocytes; diis loss cannot be attributed to contact lens‐induced hypoxia and/or oedema, or to an artifact of confocal microscopy relating to presence of residual oedema. It is postulated diat lens‐induced keratocyte loss may be related to die physical presence of contact lenses creating some mechanical effect.

Assessment of contact lens wearers’ attitude toward contact lens wear and care during Coronavirus Disease 2019 (COVID-19) pandemic: A cross-sectional online survey