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We conducted a population-based incidence study in five New England states to quantify the risk of ulcerative keratitis associated with contact lens use among aphakic persons. All practicing ophthalmologists in the five-state area were surveyed to identify prospectively all new cases of ulcerative keratitis during a 4-month period. The number of aphakic persons using specific types of contact lenses was estimated through a telephone survey of 4178 households identified by random digit dialing. The annualized incidence of ulcerative keratitis among aphakic persons using contact lenses was estimated to be 52 cases per 10,000 aphakic contact lens wearers (95% confidence interval (CI), 31.1 to 86.9). The risk of ulcerative keratitis varied substantially by lens use, with extended wear having an estimated sevenfold greater risk relative to daily wear (95% CI, 1.6 to 30.2). Rates of ulcerative keratitis in aphakic persons using contact lenses were much greater than rates among cosmetic wearers of the same lens type: for daily-wear lenses, aphakic persons were estimated to have 6.3 times the risk of cosmetic wearers (95% CI, 1.9 to 21.0), and for extended-wear lenses, aphakic persons were estimated to have 8.7 times the risk of cosmetic wearers (95% CI, 3.5 to 21.9). These risks are useful in assessing the benefits and risks of contact lens wear as an alternative to other methods of aphakic correction.

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.

The wearing of contact lenses has increased dramatically in the past decade; over 4 million people in the United States now use extended-wear soft contact lenses, and 9 million use daily-wear soft contact lenses. Numerous reports have caused concern that the use of soft contact lenses, especially extended-wear lenses, may result in a substantial risk of ulcerative keratitis. To examine this issue, we conducted a prospective study in five New England states to estimate the incidence of ulcerative keratitis among those who use cosmetic extended-wear and daily-wear soft contact lenses. To obtain the numerator for each estimate of incidence, we surveyed all practicing ophthalmologists in the study area to identify all new cases diagnosed over a four-month period. To provide the denominator, we conducted a survey of 4178 households to estimate the number of persons who wore each type of soft contact lens. The annualized incidence of ulcerative keratitis was estimated to be 20.9 per 10,000 persons using extended-wear soft contact lenses for cosmetic purposes and 4.1 per 10,000 persons using daily-wear soft contact lenses for cosmetic purposes (P less than 0.00001).