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June 2007

Comparing Contact Lens and Refractive Surgery Risks

Arch Ophthalmol. 2007;125(6):853-854. doi:10.1001/archopht.125.6.853-c

There is little doubt that the effectiveness and safety of laser-assisted in situ keratomileusis (LASIK) have improved during the past decade. However, the comparisons that Mathers et al1 drew in their letter to the Archives and the conclusions reached in comparing contact lens and LASIK safety are inadequate and misleading.

First, the assumption that a 1-year (or annualized) risk of ulcerative keratitis associated with contact lens wear can be extrapolated to estimate a 10- or 20-year risk by simply multiplying by 10 or 20 is almost certainly wrong. Imagine a 10-year contact lens wearing span for an individual. If he or she survives the first 2 years, for example, without developing a corneal ulcer, then the risk will certainly be less throughout the succeeding years. This individual is, by definition, a “survivor,” one whose underlying risk for disease is less than average. This notion is analogous to actuarial estimates of life expectancy. One's likelihood of living until age 85 years is much greater for those who have already lived until age 70 years than for those who are currently aged 25 years. Of course, the risk of ulcerative keratitis does not recede completely with time for an individual. There is some degree of underlying risk inherent to use of the device itself (and that risk is much less for daily compared with extended wear use), even for a subject who does not possess known risk factors.

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