Lisa Keay

The epidemiology of contact lens related infiltrates.

With estimated numbers of contact lens wearers worldwide exceeding 140 million, even complications with a low incidence will affect a significant number of individuals. Although contact lenses clearly have many advantages for wearers, certain risks have been associated with their use. Differences in risk for different types of contact lenses and wearing patterns have been demonstrated for both rare and common lens related complications. This review particularly focuses on the incidence and etiology of contact lens related corneal infection and inflammation. An understanding of the risks and contributory factors to these conditions is important for practitioners and will enable an informed choice of safer lens wear modalities, wear schedules, and hygiene regimes to be made.

Risk factors for moderate and severe microbial keratitis in daily wear contact lens users

OBJECTIVE To establish risk factors for moderate and severe microbial keratitis among daily contact lens (CL) wearers in Australia. DESIGN A prospective, 12-month, population-based, case-control study. PARTICIPANTS New cases of moderate and severe microbial keratitis in daily wear CL users presenting in Australia over a 12-month period were identified through surveillance of all ophthalmic practitioners. Case detection was augmented by record audits at major ophthalmic centers. Controls were users of daily wear CLs in the community identified using a national telephone survey. TESTING Cases and controls were interviewed by telephone to determine subject demographics and CL wear history. Multiple binary logistic regression was used to determine independent risk factors and univariate population attributable risk percentage (PAR%) was estimated for each risk factor. MAIN OUTCOME MEASURES Independent risk factors, relative risk (with 95% confidence intervals [CIs]), and PAR%. RESULTS There were 90 eligible moderate and severe cases related to daily wear of CLs reported during the study period. We identified 1090 community controls using daily wear CLs. Independent risk factors for moderate and severe keratitis while adjusting for age, gender, and lens material type included poor storage case hygiene 6.4× (95% CI, 1.9-21.8; PAR, 49%), infrequent storage case replacement 5.4× (95% CI, 1.5-18.9; PAR, 27%), solution type 7.2× (95% CI, 2.3-22.5; PAR, 35%), occasional overnight lens use (<1 night per week) 6.5× (95% CI, 1.3-31.7; PAR, 23%), high socioeconomic status 4.1× (95% CI, 1.2-14.4; PAR, 31%), and smoking 3.7× (95% CI, 1.1-12.8; PAR, 31%). CONCLUSIONS Moderate and severe microbial keratitis associated with daily use of CLs was independently associated with factors likely to cause contamination of CL storage cases (frequency of storage case replacement, hygiene, and solution type). Other factors included occasional overnight use of CLs, smoking, and socioeconomic class. Disease load may be considerably reduced by attention to modifiable risk factors related to CL storage case practice.

Microcyst response to high Dk/t silicone hydrogel contact lenses.

Purpose To investigate the microcyst response to extended wear (EW) with high oxygen transmissible (Dk/t) silicone hydrogel lenses. Methods Microcysts were monitored for 12 months in subjects wearing low Dk/t hydrogel lenses on a 6-night EW schedule or high Dk/t hydrogel lenses on a 30-night EW schedule. Subjects wearing low Dk/t lenses transferred to the high Dk/t EW lenses and schedule after 12 months and were monitored for a further 6 months. Results The mean number of microcysts did not deviate from baseline in the high Dk/t group. Microcysts in the low Dk/t group increased over 12 months, and more microcysts were observed in low Dk/t lens wearers compared with high Dk/t lens wearers after 3 months. Microcysts increased in 50% of subjects 1 week after transfer to high Dk/t lenses and returned to baseline levels seen with high Dk/t lens wear within 3 months. Conclusions EW with high Dk/t silicone hydrogel lenses did not cause an increase in microcyst numbers. It is not necessary to discontinue lens wear with patients who transfer from low to high Dk/t lenses because the increase in microcysts is transitory. This result has implications for practitioners when fitting and assessing the success of high Dk/t hydrogel lenses.

Trends in Fungal Keratitis in the United States, 2001 to 2007

OBJECTIVE Fungal keratitis is a serious ocular infection that is considered to be rare among contact lens wearers. The recent Fusarium keratitis outbreak raised questions regarding the background rate of Fusarium-related keratitis and other fungal keratitis in this population. DESIGN Retrospective, multicenter case series. PARTICIPANTS Six hundred ninety-five cases of fungal keratitis cases who presented to 1 of 10 tertiary medical centers from 2001 to 2007. METHODS Ten tertiary care centers in the United States performed a retrospective review of culture-positive fungal keratitis cases at their centers between January 2001 and December 2007. Cases were identified using microbiology, pathology, and/or confocal microscopy records. Information was collected on contact lens status, method of diagnosis, and organism(s) identified. The quarterly number of cases by contact lens status was calculated and Poisson regression was used to evaluate presence of trends. The Johns Hopkins Medicine Institutional Review Board (IRB) and the IRBs at each participating center approved the research. MAIN OUTCOME MEASURES Quarterly number of fungal keratitis cases and fungal species. RESULTS We identified 695 fungal keratitis cases; 283 involved the use of contact lenses. The quarterly number of Fusarium cases increased among contact lens wearers (CLWs) during the period that ReNu with MoistureLoc (Bausch & Lomb, Rochester, NY) was on the market, but returned to prior levels after withdrawal of the product from the market. The quarterly frequency of other filamentous fungi cases showed a statistically significant increase among CLWs comparing October 2004 through June 2006 with July 2006 through December 2007 with January 2001 through September 2004 (P < 0.0001). CONCLUSIONS The quarterly number of Fusarium fungal keratitis cases among CLWs returned to pre-Renu with Moistureloc levels after removal of the product from the market. However, the number of other filamentous fungal keratitis cases, although small, seems to have increased among refractive CLWs. Reasons for these apparent increases are unclear.

Risk Factors for Contact Lens Complications in US Clinical Practices

Purpose. To determine significant risk factors for any inflammatory and infectious events with soft contact lenses (SCL) in a large retrospective clinical chart review. Methods. Charts of patients who presented for SCL care from October 2005 through March 2006 were reviewed and observed for a potential of at least 2 years. Charts from those with office visits involving an event-requiring pharmacologic treatment and/or interruption of SCL wear were scanned and later adjudicated by a masked panel. Significant factors from a univariate analysis were included in a multivariate analysis for all events and subcategories of events separately. Overnight wear was not consistently recorded and was not analyzed. Results. Charts from 1276 SCL wearers comprised 4120 visits and 1454 years of SCL wear (2908 eye/yr) and included 306 events of interest in 228 patients. In a multivariate analysis, age <25 years was significantly associated with presenting any event, inflammatory events, and infectious events that may or may not be CL-related [incidence rate ratio (IRR) = 1.3; 95% CI, 1.0 to 1.7; 2.6X, 1.5 to 4.6; and 2.0X, 1.2 to 3.3, respectively]. Ametropia >5.00 D increased risk of any event (IRR = 1.5; 1.2 to 1.9) and for other infectious events (IRR = 1.9; 1.2 to 3.2). Use of daily disposable lenses associated with lid irritation (IRR = 4.5; 2.1 to 9.8) but was not significantly associated with any other type of events. New and hydrogel lens wearers had a lower incidence of all event types (IRR = 0.07; 0.01 to 0.46 and 0.77; 0.59 to 0.99, respectively). Conclusions. Eighty-two percent of these SCL wearers did not present with any complications during the observation period >2 years. The risk factors for inflammatory and infectious events among SCL wearers in clinical practice are similar to those reported in prospective clinical trials. High ametropia and age <25 years are the risk factors that impact the most types of events.

Epidemiology of contact lens-related inflammation and microbial keratitis: a 20-year perspective.

Contact lens-related keratitis has been the subject of a number of rigorous epidemiologic studies over the past 20 years. This article summarizes data from such studies that address incidence and risk factors for this condition. Estimates of risk and associated predisposing factors have been quite consistent over time, geography and study design.

Changes in myopia with low-Dk hydrogel and high-Dk silicone hydrogel extended wear

Purpose. This study compared changes in myopia between wearers of high-oxygen permeability (Dk) silicone hydrogel lenses and low-Dk hydrogel lenses after 1 year of extended wear (EW). Methods. Ninety-two adult subjects were randomly assigned to a lens type. Subjective refraction and autokeratometry were performed at baseline and at 6 and 12 months. Results. After 6 months of EW, myopia (spherical equivalent) regressed by 0.18 ± 0.33 D (p < 0.001) in the high-Dk silicone hydrogel group and progressed by −0.23 ± 0.36 D (p < 0.001) in the low-Dk hydrogel group. There were no further changes after 12 months. Previous lens wear history, baseline refractive error, and age and gender did not have an impact on the change in myopia, and only 35% of the variation could be accounted for by changes in corneal curvature and lens type. Conclusion. Soft contact lens type significantly affects the direction of change in myopia during EW. We hypothesize that these changes are driven by pressure-related redistribution of corneal tissue in high-Dk silicone hydrogel lens wearers and by hypoxia-associated corneal thinning in low-Dk hydrogel wearers. More long-term studies are required to confirm whether the effects of high-Dk silicone hydrogel lens wear on myopia are permanent.

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.

Estimating a just-noticeable difference for ocular comfort in contact lens wearers.

PURPOSE To estimate the just-noticeable difference (JND) in ocular comfort rating by human, contact lens-wearing subjects using 1 to 100 numerical scales. METHODS Ostensibly identical, new contact lenses were worn simultaneously in both eyes by 40 subjects who made individual comfort ratings for each eye using a 100-point numerical ratings scale (NRS). Concurrently, interocular preference was indicated on a five-point Likert scale (1 to 5: strongly prefer right, slightly prefer right, no preference, slightly prefer left, strongly prefer left, respectively). Differences in NRS comfort score (ΔC) between the right and left eyes were determined for each Likert scale preference criteria. The distribution of group ΔC scores was examined relative to alternative definitions of JND as a means of estimating its value. RESULTS For Likert scores indicating the presence of a slight interocular preference, absolute ΔC ranged from 1 to 30 units with a mean of 7.4 ± 1.3 (95% confidence interval) across all lenses and trials. When there was no Likert scale preference expressed between the eyes, absolute ΔC did not exceed 5 units. CONCLUSIONS For ratings of comfort using a 100-point numerical rating scale, the inter-ocular JND is unlikely to be less than 5 units. The estimate for the average value in the population was approximately 7 to 8 units. These numbers indicate the lowest level at which changes in comfort measured with such scales are likely to be clinically significant.

Unintentional injury mortality in India, 2005: Nationally representative mortality survey of 1.1 million homes

BackgroundUnintentional injuries are an important cause of death in India. However, no reliable nationally representative estimates of unintentional injury deaths are available. Thus, we examined unintentional injury deaths in a nationally representative mortality survey.MethodsTrained field staff interviewed a living relative of those who had died during 2001-03. The verbal autopsy reports were sent to two of the130 trained physicians, who independently assigned an ICD-10 code to each death. Discrepancies were resolved through reconciliation and adjudication. Proportionate cause specific mortality was used to produce national unintentional injury mortality estimates based on United Nations population and death estimates.ResultsIn 2005, unintentional injury caused 648 000 deaths (7% of all deaths; 58/100 000 population). Unintentional injury mortality rates were higher among males than females, and in rural versus urban areas. Road traffic injuries (185 000 deaths; 29% of all unintentional injury deaths), falls (160 000 deaths, 25%) and drowning (73 000 deaths, 11%) were the three leading causes of unintentional injury mortality, with fire-related injury causing 5% of these deaths. The highest unintentional mortality rates were in those aged 70years or older (410/100 000).ConclusionsThese direct estimates of unintentional injury deaths in India (0.6 million) are lower than WHO indirect estimates (0.8 million), but double the estimates which rely on police reports (0.3 million). Importantly, they revise upward the mortality due to falls, particularly in the elderly, and revise downward mortality due to fires. Ongoing monitoring of injury mortality will enable development of evidence based injury prevention programs.