title: Symmetry of refractive and visual acuity outcome in the Prospective Evaluation of Radial Keratotomy (PERK) study.
abstract: In the Prospective Evaluation of Radial Keratotomy (PERK) study, the symmetry of refractive and visual acuity outcome was analyzed in 269 patients with bilateral radial keratotomy with a single operation in each eye. Patients were required to wait 1 year after surgery on the first eye before having surgery on the second eye. At 1 year after surgery on the second eye, 98% of patients had 3.00 diopters or less difference between their two eyes in the spherical equivalent of the cycloplegic refraction (100% before surgery), and 96% of patients had 3.00 D or less difference between their two eyes in the amount of refractive power in the vertical meridian (100% before surgery). Thus, surgically induced refractive anisometropia was not a major complication in the PERK study. However, 14% of patients had four to eight Snellen lines difference in the uncorrected visual acuity between their two eyes (1% before surgery), emphasizing that induced asymmetry of refraction is a potential clinical problem for some patients.
authors.affiliation: PERK Statistical and Clinical Coordinating Centers, Emory University School of Medicine, Atlanta, Ga.
authors.forename: M J
authors.initials: MJ
authors.lastname: Lynn
authors.forename: G O
authors.initials: GO
authors.lastname: Waring
authors.forename: A
authors.initials: A
authors.lastname: Nizam
authors.forename: M H
authors.initials: MH
authors.lastname: Kutner
authors.forename: W
authors.initials: W
authors.lastname: Culbertson
authors.forename: M B
authors.initials: MB
authors.lastname: McDonald
authors.forename: W D
authors.initials: WD
authors.lastname: Meyers
authors.forename: M A
authors.initials: MA
authors.lastname: Naidoff
authors.forename: J D
authors.initials: JD
authors.lastname: Nelson
authors.forename: S A
authors.initials: SA
authors.lastname: Obstbaum
mesh_terms: D000328:Adult; D015858:Anisometropia / Q000209:etiology; D001251:Astigmatism / Q000209:etiology; D006801:Humans; D007646:Keratotomy, Radial / Q000009:adverse effects*; D008297:Male; D011300:Preoperative Care; D011379:Prognosis; D011446:Prospective Studies; D012030:Refractive Errors / Q000209:etiology*; D014792:Visual Acuity