The aim of this grant is to examine 435 core and 97 pilot patients (a total of 953 eyes) ten years after surgery in the Prospective Evaluation of Radial Keratotomy (PERK) study. These patients received radial keratotomy and were followed for five years in the initial phase of the PERK study from 1983-1989. Because radial keratotomy is the most frequently performed refractive corneal surgical procedure -- 150,000 or more operations being done annually in the United States -- hundreds of thousands being done worldwide, it is important to document the efficacy, safety, stability and predictability of radial keratotomy over the long term. 1) What are the results for major outcome variables: 1) cycloplegic and manifest (fogging technique) refraction, corrected and uncorrected visual acuity (NEI charts), central keratometric power (Bausch & Lomb keratometer), intraocular pressure and corneal thickness (ultrasonic pachometry)? 2) How have the refraction and visual acuity changed from five to ten years and what is the stability of the approximately 25% of eyes that showed a continued increase in the effect of the surgery between six months and four years? 3) How many eyes have lost two or more Snellen lines of spectacle corrected visual acuity compared to baseline and what other complications have arisen? 4) Are endothelial changes detectable by small-field and large-field specular microscopy with morphometric analysis? 5) What is the topography of the cornea after radial keratotomy as determined by computer- assisted videokeratography, and how do the aspheric corneal optics affect visual acuity and refraction as measured by refraction through fixed aperatures? 6) How does contrast sensitivity after radial keratotomy compare to that in the contralateral unoperated eye of the same patient and to that in age and refraction matched controls? 7) Can clinically meaningful amounts of glare be detected as measured by sine-wave gratings or Pelli-Robson charts? 8) What is the level of subjective patient satisfaction as determined by formal psychometric testing? 9) What is the pattern of glasses and contact lens wearing? Because of the intense effort to maintain the PERK population between the five and ten-year examinations, a 90% follow-up rate is expected. Nine clinical centers under the direction of an ophthalmologist principal investigator, with a coordinator- technician, will perform the standardized examinations during 1993. Patients living outside the metropolitan area of a PERK center will be returned to a center for examination.
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