title: Relationship between refractive error and visual acuity in the Prospective Evaluation of Radial Keratotomy (PERK) Study.
abstract: As part of the Prospective Evaluation of Radial Keratotomy (PERK) study, we examined the relationship between post-operative refractive error and visual acuity without correction. We included 394 eyes (one eye per patient) with refractive errors ranging from -3.00 to +3.00 diopters one year after radial keratotomy. Within each 1-D range of the spherical equivalent of the refractive error, the visual acuity spanned five to ten Snellen lines. For visual acuities of 20/16 to 20/50, the refractive error spanned 3 to 5 D. Additionally, operated eyes had a better average uncorrected visual acuity than unoperated eyes with a similar refractive error. Within the narrow range of refraction between -2.00 and -2.50 D, the mean uncorrected visual acuity was 20/125 for 56 unoperated eyes and 20/63 for 29 operated eyes, a difference of three Snellen lines.
mesh_terms: D000328:Adult; D000375:Aging; D001251:Astigmatism / Q000503:physiopathology; D006801:Humans; D007646:Keratotomy, Radial / Q000592:standards*; D008875:Middle Aged; D011446:Prospective Studies; D012030:Refractive Errors / Q000503:physiopathology*; D054140:Refractive Surgical Procedures; D014792:Visual Acuity