Review of 20 years of soft contact lens wearer ocular physiology data.

BACKGROUND: Since the introduction of Silicone hydrogel (SiHy) contact lenses 20 years ago, industry has continued to modify lens materials, designs, lens care products and manufacturing processes, striving to improve contact lens physiological performance, comfort, and convenience for wearers. The purpose of this study was to investigate whether the ocular health of habitual soft contact lens wearers today is better than it was in previous decades. METHODS: Baseline ocular physiology data for 3624 participants from a The Brien Holden Vision Institute clinical trials database were retrospectively reviewed. Records were grouped into 3 time periods; A: >2 decades ago (1997-1999), B: one decade ago (2009-2014) and C: recent years (since 2015). Physiology data for both neophytes and habitual contact lens wearers included; bulbar, limbal and upper palpebral conjunctival redness, corneal and conjunctival staining and conjunctival indentation from contact lenses. RESULTS: Corneal staining levels are similar between neophytes and contact lens wearers at time points A and C but worse for contact lens wearers at time point B. Limbal redness was greater in contact lens wearers than in neophytes at time point A but at time points B and C they are not different to the non-contact lens wearing population. In recent years, most ocular physiological variables in habitual contact lens wearers are similar to neophytes. CONCLUSIONS: While there have been changes over the past two decades in ocular physiological responses to contact lens wear, it appears that ocular health with current day contact lens wear is similar to no lens wear in most respects.

Corneal dendritic cells and the subbasal nerve plexus following neurotoxic treatment with oxaliplatin or paclitaxel.

Immune cell infiltration has been implicated in neurotoxic chemotherapy for cancer treatment. However, our understanding of immune processes is still incomplete and current methods of observing immune cells are time consuming or invasive. Corneal dendritic cells are potent antigen-presenting cells and can be imaged with in-vivo corneal confocal microscopy. Corneal dendritic cell densities and nerve parameters in patients treated with neurotoxic chemotherapy were investigated. Patients treated for cancer with oxaliplatin (n = 39) or paclitaxel (n = 48), 3 to 24 months prior to assessment were recruited along with 40 healthy controls. Immature (ImDC), mature (MDC) and total dendritic cell densities (TotalDC), and corneal nerve parameters were analyzed from in-vivo corneal confocal microscopy images. ImDC was increased in the oxaliplatin group (Median, Md = 22.7 cells/mm2) compared to healthy controls (Md = 10.1 cells/mm2, p = 0.001), but not in the paclitaxel group (Md = 10.6 cells/mm2). ImDC was also associated with higher oxaliplatin cumulative dose (r = 0.33, p = 0.04) and treatment cycles (r = 0.40, p = 0.01). There was no significant difference in MDC between the three groups (p > 0.05). Corneal nerve parameters were reduced in both oxaliplatin and paclitaxel groups compared to healthy controls (p < 0.05). There is evidence of elevation of corneal ImDC in oxaliplatin-treated patients. Further investigation is required to explore this potential link through longitudinal studies and animal or laboratory-based immunohistochemical research.

Tessellated fundus appearance and its association with myopic refractive error.

The appearance of tessellated fundus in an eye may act as a marker in identifying visual performance, degree of myopia or risk of progression of myopia in a given eye. A systematic literature search using key words was performed using PubMed, Web of Science and Google Scholar and of the 832 studies identified, 10 full-length articles, which met the inclusion criteria, were considered for review. The primary outcome measures were association of tessellated fundus with: (i) visual acuity, (ii) refractive error, (iii) axial length, (iv) choroidal thickness and (v) future progression of myopia when compared to either no myopic maculopathy, or more severe myopic maculopathy. There was no significant difference in the visual acuity noted between eyes with normal fundus and tessellated fundus appearance. Compared to eyes with tessellated fundus, eyes with more severe myopic maculopathy had a four-line decrease in best-corrected visual acuity, more myopia (mean difference 2.75 D, range 0.28-5.78 D) and a longer axial length (mean difference 2 mm, range 2.29 to 1.71 mm). Eyes with tessellated fundus generally exhibited a significant decrease in choroidal thickness compared to eyes with no maculopathy. In mostly older individuals, eyes with tessellated fundus had a better outcome with respect to visual acuity, degree of myopia and axial length compared to other severe myopic maculopathies, but had a worse outcome for choroidal thickness and degree of myopia, compared to eyes with no myopic maculopathy. The features such as reduced choroidal thickness combined with a predilection to infra-temporal and parapapillary regions may indicate regions of stress that are prone to more stretching/atrophic changes. This systematic review demonstrated an association of tessellated fundus with visual acuity, refractive error, axial length and choroidal thickness and hence emphasises the documentation of the presence and location of tessellated fundus appearance that may help in predicting the progression of myopia.

Potential Lost Productivity Resulting from the Global Burden of Myopia: Systematic Review, Meta-analysis, and Modeling.

PURPOSE: We estimated the potential global economic productivity loss resulting from vision impairment (VI) and blindness as a result of uncorrected myopia and myopic macular degeneration (MMD) in 2015. CLINICAL RELEVANCE: Understanding the economic burden of VI associated with myopia is critical to addressing myopia as an increasingly prevalent public health problem. METHODS: We estimated the number of people with myopia and MMD corresponding to critical visual acuity thresholds. Spectacle correction coverage was analyzed against country-level variables from the year of data collection; variation in spectacle correction was described best by a model based on a human development index, with adjustments for urbanization and age. Spectacle correction and myopia data were combined to estimate the number of people with each level of VI resulting from uncorrected myopia. We then applied disability weights, labor force participation rates, employment rates, and gross domestic product per capita to estimate the potential productivity lost among individuals with each level and type of VI resulting from myopia in 2015 in United States dollars (US$). An estimate of care-associated productivity loss also was included. RESULTS: People with myopia are less likely to have adequate optical correction if they are older and live in a rural area of a less developed country. The global potential productivity loss associated with the burden of VI in 2015 was estimated at US$244 billion (95% confidence interval [CI], US$49 billion-US$697 billion) from uncorrected myopia and US$6 billion (95% CI, US$2 billion-US$17 billion) from MMD. Our estimates suggest that the Southeast Asia, South Asia, and East Asia Global Burden of Disease regions bear the greatest potential burden as a proportion of their economic activity, whereas East Asia bears the greatest potential burden in absolute terms. CONCLUSIONS: Even under conservative assumptions, the potential productivity loss associated with VI and blindness resulting from uncorrected myopia is substantially greater than the cost of correcting myopia.

Profile of off-axis higher order aberrations and its variation with time among various refractive error groups.

Peripheral higher order aberrations (HOA) of 646 children at 30° temporal, nasal and inferior visual field were measured under cycloplegia (5 mm pupil diameter) using a commercially available Shack-Hartmann aberrometer in the Sydney Myopia Study [age, 12.7 ±â€¯0.4 years (mean ±â€¯standard deviation)] and five years later in the Sydney Adolescent Vascular and Eye Study. At baseline, 176 eyes were emmetropic, 95 were myopic and 375 were hyperopic. Coma, 3rd order and RMS of coma increased with eccentricity for all eyes and no difference was observed for 4th order and RMS of C(4,0) among refractive error groups. More positive C(4,0) was observed for hyperopic eyes at periphery. At follow up, 26% had 'myopic change' and 70% had 'no change' in refractive error. At follow-up, horizontal coma became more negative at nasal field and more positive at temporal field for all eyes. More positive C(4,0) for hyperopic eyes at baseline may indicate variation in optical characteristics of peripheral cornea and crystalline lens. An increase in horizontal coma with time, irrespective of refractive error change, may be attributed to variation in the shape factor of peripheral cornea and crystalline lens and/or misalignment of optical surfaces/components relative to the visual axis (angle kappa) as the eye grows in axial length.

Global prevalence of visual impairment associated with myopic macular degeneration and temporal trends from 2000 through 2050: systematic review, meta-analysis and modelling.

PURPOSE: We used systematic review and meta-analysis to identify and assimilate evidence quantifying blindness and visual impairment (VI) associated with myopic macular degeneration (MMD), then derived models to predict global patterns. The models were used to estimate the global prevalence of blindness and VI associated with MMD from 2000 to 2050. METHODS: The systematic review identified 17 papers with prevalence data for MMD VI fitting our inclusion criteria. Data from six papers with age-specific data were scaled to relative age-dependent risk and meta-analysed at VI and blindness levels. We analysed variance in all MMD VI and blindness data as a proportion of high myopia against variables from the place and year of data collection, with a model based on health expenditure providing the best correlation. We used this model to estimate the prevalence and number of people with MMD VI in each country in each decade. RESULTS: We included data from 17 studies comprising 137 514 participants. We estimated 10.0 million people had VI from MMD in 2015 (prevalence 0.13%, 95% CI 5.5 to 23.7 million, 0.07% to 0.34%), 3.3 million of whom were blind (0.04%, 1.8 to 7.8 million, 0.03% to 0.10%). We estimate that by 2050, without changing current interventions, VI from MMD will grow to 55.7 million people (0.57%, 29.0 to 119.7 million, 0.33% to 1.11%), 18.5 million of whom will be blind (0.19%, 9.6 to 39.7 million, 0.11% to 0.37%). CONCLUSION: The burden of MMD blindness and VI will rise significantly without efforts to reduce the development and progression of myopia and improve the management of MMD.

Global Prevalence of Myopia and High Myopia and Temporal Trends from 2000 through 2050.

PURPOSE: Myopia is a common cause of vision loss, with uncorrected myopia the leading cause of distance vision impairment globally. Individual studies show variations in the prevalence of myopia and high myopia between regions and ethnic groups, and there continues to be uncertainty regarding increasing prevalence of myopia. DESIGN: Systematic review and meta-analysis. METHODS: We performed a systematic review and meta-analysis of the prevalence of myopia and high myopia and estimated temporal trends from 2000 to 2050 using data published since 1995. The primary data were gathered into 5-year age groups from 0 to ≥100, in urban or rural populations in each country, standardized to definitions of myopia of -0.50 diopter (D) or less and of high myopia of -5.00 D or less, projected to the year 2010, then meta-analyzed within Global Burden of Disease (GBD) regions. Any urban or rural age group that lacked data in a GBD region took data from the most similar region. The prevalence data were combined with urbanization data and population data from United Nations Population Department (UNPD) to estimate the prevalence of myopia and high myopia in each country of the world. These estimates were combined with myopia change estimates over time derived from regression analysis of published evidence to project to each decade from 2000 through 2050. RESULTS: We included data from 145 studies covering 2.1 million participants. We estimated 1406 million people with myopia (22.9% of the world population; 95% confidence interval [CI], 932-1932 million [15.2%-31.5%]) and 163 million people with high myopia (2.7% of the world population; 95% CI, 86-387 million [1.4%-6.3%]) in 2000. We predict by 2050 there will be 4758 million people with myopia (49.8% of the world population; 3620-6056 million [95% CI, 43.4%-55.7%]) and 938 million people with high myopia (9.8% of the world population; 479-2104 million [95% CI, 5.7%-19.4%]). CONCLUSIONS: Myopia and high myopia estimates from 2000 to 2050 suggest significant increases in prevalences globally, with implications for planning services, including managing and preventing myopia-related ocular complications and vision loss among almost 1 billion people with high myopia.

The effect of compliance on contact lens case contamination.

PURPOSE: To determine the efficacy of written instructions on contact lens case hygiene and to quantify the effect of noncompliance on contact lens case contamination. METHODS: Data were retrospectively analyzed from 16 prospective, 3-month daily-wear studies during which six commercially available silicone hydrogel contact lenses and seven lens care solutions (LCS) were tested following a similar protocol. Verbal instructions regarding case hygiene (rinse case with LCS, not tap water) were given in nine studies, while the same instructions were given verbally and in written format in seven studies. A survey on contact lens, LCS, and lens case hygiene was completed at 1- and 3-month visits and compliance with case hygiene instructions was determined. Regular contact lens cases were used for 1 month and collected for microbial analysis at the 1- and 3-month visits. The rate of case contamination and the types of microbes contaminating cases were evaluated. RESULTS: Participants given verbal and written instructions were more likely to be compliant with case hygiene instructions than those just given verbal instructions (odds ratio [OR]: 2.19, p < 0.001, 95% confidence interval [CI]: 1.40-3.44). The overall case contamination rate was 79%. Use of tap water to rinse contact lens cases was associated with significantly more cases contaminated with Gram-negative bacteria (GNB) (30% vs. 10%, p < 0.001), a greater risk of GNB case contamination (OR: 2.91, p < 0.001. 95% CI: 1.72-4.92), and a higher quantity of GNB in cases (mean colony-forming unit/case ± SD: 28,286 ± 131,935 vs. 6477 ± 60,447, p < 0.001). CONCLUSIONS: Lens case hygiene can be improved by effective communication of instructions. Contact lens wearers should be actively discouraged from rinsing contact lens cases with tap water because of the increased risk of GNB contamination.

Spectacle compliance amongst rural secondary school children in Pune district, India.

BACKGROUND: Refractive errors (RE) are the most common cause of avoidable visual impairment in children. But benefits of visual aids, which are means for correcting RE, depend on the compliance of visual aids by end users. AIM: To study the compliance of spectacle wear among rural school children in Pune district as part of the sarva siksha abhiyan (education for all scheme) after 6 - 12 months of providing free spectacles. SETTINGS AND DESIGN: Cross-sectional follow-up study of rural secondary school children in western India. MATERIALS AND METHODS: The students were examined by a team of optometrists who collected the demographic details, observed if the child was wearing the spectacles, and performed an ocular examination. The students were asked to give reasons for non-wear in a closed-ended questionnaire. STATISTICAL ANALYSIS: Chi-square test and multiple logistic regression used for data analysis. RESULTS: Of the 2312 students who were dispensed spectacles in 2009, 1018 were re-examined in 2010. 523 students (51.4%) were female, the mean age was 12.1 years 300 (29.5%) were wearing their spectacles, 492 (68.5%) students claimed to have them at home while 211 (29.4%) reported not having them at all. Compliance of spectacle wear was positively associated to the magnitude of refractive error (P < 0.001), father's education (P = 0.016), female sex (P = 0.029) and negatively associated to the visual acuity of the better eye (P < 0.001) and area of residence (P < 0.0001). Of those that were examined and found to be myopic (N = 499), 220 (44%) wore their spectacles to examination. Factors associated with compliance to spectacle usage in the myopic population included increasing refractive error (P < 0.001), worsening visual acuity (P < 0.001), and higher academic performance (P < 0.001). The causes for not wearing spectacles were 'lost spectacles' 67(9.3%), 'broken spectacles' 125 (17.4%), 'forgot spectacles at home' 117 (16.3%), 'uses spectacles sometimes' 109 (15.2%), 'teased about spectacles' 142 (19.8%) and 'do not like the spectacles' 86 (12%). CONCLUSION: Spectacle compliance was poor amongst school children in rural Pune; many having significant vision loss as a result.

External ocular surface and lens microbiota in contact lens wearers with corneal infiltrates during extended wear of hydrogel lenses.

OBJECTIVES: To determine whether carriage of microbes on the contact lens or ocular surfaces during extended wear (EW) with soft hydroxyethyl methacrylate (HEMA)-based contact lenses predisposes the wearer to adverse events. METHODS: Participants (non-contact lens wearers) were enrolled in a clinical study involving wear of HEMA-based hydrogel lenses on a six night EW basis with weekly replacement. Type and number of bacteria colonizing the lower lid margins, upper bulbar conjunctiva, and contact lenses during EW after one night, 1 week, 1 month, and thereafter every 3 months for 3.5 years were determined. The association of bacteria with adverse responses was compared between carriers (defined as having significant microbes cultured from two or more samples with 1 year) and noncarriers, and the strength of the association was estimated using multivariate logistic regression. RESULTS: Carriers of gram-positive bacteria on lenses (particularly coagulase negative staphylococci or Corynebacterium spp.) were approximately three and eight times more likely to develop contact lens-induced peripheral ulcers (CLPUs) and asymptomatic infiltrates (AIs), respectively. Staphylococcus aureus was most frequently isolated from lenses during CLPU. Carriers of gram-negative bacteria on lenses were five times more likely to develop contact lens-induced acute red eye (CLARE). Haemophilus influenzae was isolated most frequently from lenses during CLARE and AI events. CONCLUSIONS: Bacterial carriage on contact lenses during EW predisposes the wearer to the development of corneal inflammatory events including CLARE, CLPU, and AI.

Risk factors for physical discomfort in Australian optometrists.

PURPOSE: There are anecdotal reports that optometrists suffer work-related physical discomfort but no published reports to support this. METHODS: An on-line questionnaire was sent by e-mail to ∼1700 Australian optometrists. Participants were asked if they experienced work-related discomfort in any of eight nominated body regions, the type and severity of discomfort, self-reported work-related factors contributing to the discomfort, and demographic and work-related information. RESULTS: Four hundred sixteen optometrists participated in the questionnaire. Work-related physical discomfort was reported by 82% of respondents. The most common sites of discomfort were neck, shoulder, and lower back. Univariate analysis revealed that females are more likely to report discomfort than males (p = 0.001) and more likely to report a higher number of discomfort sites (p = 0.002). Multivariate analysis revealed that females have up to a 6.6× [confidence interval (CI) = 2.2-19.9] greater risk of reporting discomfort in individual body locations compared with males and a higher risk of experiencing severe discomfort (discomfort present for >30 days) [odds ratio (OR) = 3.0, CI = 1.7 to 5.5]. A greater number of eye examinations per day increased the risk of reporting work-related discomfort by up to 5.1× (CI = 2.1 to 12.7). Being self-employed and being older than 40 years both appear to be protective factors for work-related discomfort. The risk of experiencing severe discomfort is increased by performing repetitive tasks (OR = 1.9, CI = 1.2 to 3.1) and by continuing to work while injured (OR = 2.9, CI = 1.6 to 5.2). Eliminating both these factors would reduce the disease load for severe discomfort by 28%. CONCLUSIONS: Females, young optometrists, and those conducting a high number of consultations daily have a higher risk of experiencing work-related physical discomfort. Performing repetitive tasks and continuing to work while injured increases the risk of severe discomfort. The results of this investigation have important implications for the longevity of the optometry workforce.

Corneal erosions, bacterial contamination of contact lenses, and microbial keratitis.

OBJECTIVES: To estimate the rate of corneal erosion coupled with gram-negative bacterial contamination of contact lenses and compare this with the rate of microbial keratitis (MK) with contact lenses. METHODS: The rate of corneal erosion and contact lens contamination by gram-negative bacteria were calculated from several prospective trials. These rates were used to calculate the theoretical rate of corneal erosion happening at the same time as wearing a contact lens contaminated with gram-negative bacteria. This theoretical rate was then compared with the rates of MK reported in various epidemiological and clinical trials. RESULTS: Corneal erosions were more frequent during extended wear (0.6-2.6% of visits) compared with daily wear (0.01-0.05% of visits). No corneal erosions were observed for lenses worn on a daily disposable basis. Contamination rates for lenses worn on a daily disposable basis were the lowest (2.4%), whereas they were the highest for low Dk lenses worn on an extended wear basis (7.1%). The estimated rate of corneal erosions occurring at the same time as wearing lenses contaminated with gram-negative bacteria was the lowest during daily wear of low Dk lenses (1.56/10,000 [95% CI: 0.23-10.57]) and the highest during extended wear of high Dk lenses (38.55/10,000 [95% CI: 24.77-60.04]). These rates were similar in magnitude to the rates reported for MK of different hydrogel lenses worn on differing wear schedules. CONCLUSION: The coincidence of corneal erosions during lens wear with gram-negative bacterial contamination of lenses may account for the relative incidence of MK during lens wear with different lens materials and modes of use.

Contact lens-related adverse events and the silicone hydrogel lenses and daily wear care system used.

OBJECTIVE: To investigate the incidence of adverse events related to the use of varying silicone hydrogel contact lens and lens solution combinations. METHODS: Individuals with myopia (N = 558) participated in 1 or more of approximately 40-participant trials in a matrix of 20 silicone hydrogel contact lens and lens-solution combinations. Visits were at baseline, 2 weeks, 1 month, and 3 months. The mean study completion rate was 90% of the expected participant-months (final data set: 840 lens-solution combinations and 2271 participant-months). Adverse events were reported as the first occurrence of each type per 100 participant-months for each lens-solution combination. RESULTS: The rate of all corneal infiltrative events (CIEs) was 3.1 per 100 participant-months (range, 0-10.5), and the rate of symptomatic CIEs was 1.7 per 100 participant-months (range, 0-10.5), including 1 case of microbial keratitis (0.04 per 100 participant-months). Rates for CIEs differed substantially among solution groups, with hydrogen peroxide having the lowest rate (0.6 per 100 participant-months; range, 0-0.9). The rate was 0.8 per 100 participant-months (range, 0-8.0) for superior epithelial arcuate lesions, which varied by lens type, 0.04 per 100 participant-months (1 case only) for corneal erosion, and 0.4 per 100 participant-months (range, 0-2.0) for contact lens papillary conjunctivitis, which was modified by type of solution. The rate of solution-induced corneal staining for all lens-solution combinations was 4.7 per 100 participant-months (range, 0-23) and varied significantly based on lens-solution combination (P < .001). CONCLUSIONS: The frequency of adverse events varied with silicone hydrogel contact lens and lens solution combinations, with hydrogen peroxide having the lowest incidence of CIEs and solution-induced corneal staining, indicating that lens material and design, type of solution, and solution-lens interactions are likely contributing factors in this mode of lens wear.

Monochromatic aberrations in hyperopic and emmetropic children.

We investigated differences in higher order monochromatic aberrations between hyperopic and emmetropic eyes from two large cohorts (mostly 6 and 12 year old) of Caucasian children. Additionally, we investigated the differences of higher order monochromatic aberrations between age groups. In both cohorts, hyperopic eyes had significantly higher levels of positive spherical aberration (SA) and higher orders (HO) RMS than emmetropic eyes. Higher levels of positive SA were also found in the older cohort (irrespectively of the refractive error) although this difference was statistically significant only for emmetropic, low hyperopic and moderate hyperopic eyes. The observed higher levels of positive SA found in hyperopic eyes could explain for the previously reported differences in accommodative responses between hyperopic and non-hyperopic eyes. Our results provide some evidence of a relationship between ocular changes that typically occur during eye growth and the observed levels of higher order aberrations in children eyes.

Are inflammatory events a marker for an increased risk of microbial keratitis?

PURPOSE: To consider whether inflammatory events, such as contact lens-induced peripheral ulcers, contact lens-induced acute red eye, and infiltrative keratitis are a marker for an increased risk for the occurrence of microbial keratitis. METHODS: A review of relevant studies was undertaken with the view to answering two questions: 1) Do inflammatory events associated with contact lens wear progress to infection or microbial keratitis; and 2) Do episodes of inflammatory events predispose a patient to having an event of microbial keratitis? RESULTS: The large body of laboratory work, along with the epidemiologic data on incidence rates and clinical data with regard to differences between the nature of inflammatory events and infection, supports the supposition that inflammatory events are not a marker for increased risk of microbial keratitis. CONCLUSIONS: Inflammatory events are not a marker for increased risk of microbial keratitis, nor will they progress to infection because they are separate disease entities.

Two presentations of contact lens-induced papillary conjunctivitis (CLPC) in hydrogel lens wear: local and general.

PURPOSE: The purpose of this study was to confirm that two distinct clinical presentations of contact lens-induced papillary conjunctivitis (CLPC), local and general, occur in hydrogel lens wear. METHODS: Retrospective analyses of 124 CLPC events were identified. The classification of CLPC was based on location and extent of papillae. CLPC was classified as local if papillae were present in one to two areas of the tarsal conjunctiva and general if papillae occurred in three or more areas. The CLPC events were compared with an asymptomatic control group in prospective clinical trials conducted from 1993 until 2003 at two clinical sites, Australia and India. Two hundred sixteen subjects from Australia and 914 subjects from India wore either high Dk silicone hydrogel or low Dk hydrogel lenses on a 6-night (6N) or 30-night extended-wear (EW) schedule. The physiological responses of the ocular surface, including tarsal conjunctiva redness and roughness, number of papillae present, lens fit and performance, and subjective patient symptoms, were measured during each visit at each site. These variables listed were compared between local CLPC groups and asymptomatic controls and general CLPC groups and asymptomatic controls. RESULTS: Two types of CLPC in hydrogel lens wearers have been confirmed. Of the 124 CLPC events, there were 61 local and 63 general events. Local and general CLPC cases reported significantly greater frequency of symptoms compared with the asymptomatic controls, in particular itching, lens awareness, secretion, and blurred vision (p < 0.1). CONCLUSIONS: The classification of CLPC into two types, local and general, in hydrogel lens wear was confirmed based on presentations at both sites. This distribution of papillae between local and general CLPC may indicate separate etiologies involved in the pathogenesis of the condition.

Microbial keratitis in prospective studies of extended wear with disposable hydrogel contact lenses.

PURPOSE: To report the annualized incidence of microbial keratitis with extended wear of low oxygen transmissible (Dk/t) disposable soft contact lenses from prospective postmarket clinical trials. METHODS: Seven hundred ninety subjects were enrolled at the L.V. Prasad Eye Institute (LVPEI), Hyderabad, India from March 1993 to March 2000, resulting in 1231 patient eye years, and 167 subjects were enrolled at the Cornea and the Contact Lens Research Unit (CCLRU), Sydney, Australia from July 1987 to December 1999, resulting in 842 patient eye years. RESULTS: The annualized incidence of microbial keratitis per 10,000 eyes per year of lens wear was 32.5 (95% CI 8.9 to 83.2) for LVPEI, 23.8 (95% CI=2.9 to 85.8) for CCLRU; when data are combined across both centers, the incidence was 28.9 (95% CI=10.6 to 63) per 10,000 eyes per year of lens wear. This equates to 57.0 per 10,000 wearers or 1 in 173 wearers per year of lens wear. All events were rated as slight to moderate in severity and did not result in visual loss. Two events were described to highlight the challenges in diagnosis and treatment of microbial keratitis. CONCLUSIONS: The incidence of microbial keratitis with extended wear of low-Dk/t disposable lenses was higher in these prospective studies (1 in 210 wearers per year at CCLRU and 1 in 154 wearers per year at LVPEI) than that seen in retrospective population-based surveillance studies (1 in 500 wearers per year). Practitioners and patients should always be alert to signs and symptoms, and practitioners should adopt conservative strategies for diagnosis and management of contact lens-related adverse events.

Comparison of the performance of 6- or 30-night extended wear schedules with silicone hydrogel lenses over 3 years.

AIM: To compare the clinical performance of silicone hydrogel lenses worn for 6- or 30-nights, with monthly replacement, for 3 years. METHODS: In this 3-year prospective clinical trial, 161 subjects were enrolled and 154 commenced extended wear. Clinical performance was assessed by comparing discontinuations and lens surface characteristics (front surface deposits, lens wettability, number of mucin balls), lens fitting performance (primary gaze movement, lens tightness), and physiologic parameters (limbal and bulbar redness, corneal and conjunctival staining, microcysts) and subjective parameters (ratings of comfort and vision) between groups. RESULTS: Eighty-eight subjects remained in the study after 36 months. There were no differences in the probability of subjects surviving in either group, and the major cause of lens-related discontinuation in both groups was contact lens-induced papillary conjunctivitis. There were no clinically important differences in performance between wear schedules. CONCLUSION: The long-term clinical performance of silicone hydrogels worn for 6- or 30-nights continuously was similar. Clinical markers of hypoxia were low in both groups, and the 6-night wear schedule was not superior to the 30-night wear schedule with regard to preventing lens spoilage, improving corneal physiology, or subjective symptoms of comfort and vision.

Mucin balls with wear of conventional and silicone hydrogel contact lenses.

PURPOSE: To compare the frequency of mucin balls in subjects wearing conventional and high-Dk silicone hydrogel lenses during 12 months of extended-wear and to determine whether mucin balls are associated with any lens or subject characteristics. METHODS: This study used data from a clinical trial where subjects wore either conventional hydrogel (N = 69, 6-night extended-wear) or silicone hydrogel (N = 70, 30-night extended-wear) contact lenses for 12 months. The number of mucin balls and other physiological responses, lens fit and performance, and subjective patient responses to lens wear were rated at each scheduled visit. RESULTS: Subjects in the silicone hydrogel group had significantly greater numbers of mucin balls compared with subjects in the conventional hydrogel group over time (p < 0.001), but there were no significant differences in the percentage of subjects with mucin balls between the two groups. Increasing lens wettability, back surface deposits, and time of lens wear were associated with higher numbers of mucin balls in the conventional hydrogel group (p < 0.05); steeper corneal curvature and increasing lens wettability, back surface deposits, and number of microcysts were associated with higher numbers of mucin balls in the silicone hydrogel group (p < 0.05). CONCLUSIONS: This study indicates that a subset of the population is predisposed to develop mucin balls irrespective of the soft contact lens type worn, but lens type influences the degree of mucin ball formation. The relationship between lens wettability, back surface deposits, and steeper corneal curvature with mucin balls supports the hypothesis that the mechanical interaction of a lens with the surface layer of the epithelium and the tear film in association with the blinking forces of the lid is involved in mucin ball formation.