Comparison of prevalence rates for lens opacities among studies is difficult because of different populations and different definitions of cataract severity.1 The rates of 2.1% to 8.5% quoted by Dr Gwon were for different race-gender groups for patients 45 to 64 years old in the NHANES study.2 We were unable to verify the rate of 6% among subjects 40 to 49 years of age that Dr Gwon attributed to the Waterman reference.3 Also, the rate of 12.2% in the NHANES study quoted by Dr Gwon was for all lens opacities among subjects aged 45 to 54 years; the rate for lens opacities causing visual loss of 20/25 or worse was 2.6%.4At 10 years in the PERK Study, the lens opacity was subjectively judged by the examiner on a five-point scale (none, trace, mild, moderate, or severe). We did not employ a formal lens
Lynn MJ, Waring GO. Prospective Evaluation of Radial Keratotomy (PERK) Study 10 Years After Surgery-Reply. Arch Ophthalmol. 1995;113(10):1225–1226. doi:10.1001/archopht.1995.01100100013003
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