Comprehensive method of analyzing the results of photoastigmatic refractive keratectomy for the treatment of post-cataract myopic anisometropia

Purpose: To assess the efficacy, stability, and safety of photoastigmatic refractive keratectomy (PARK) in treating post-cataract myopic anisometropia to restore binocularity and to describe a comprehensive method for analyzing the results of refractive Surgery. Setting: St. Paul's Eye Center, Royal Liverpool Hospital, Liverpool, United Kingdom. Methods: Nineteen patients (20 eyes) with post-cataract myopic anisometropia were treated with PARK using a VISX Twenty-Twenty laser and followed for 12 months. Cataract surgery had been performed between 10 and 144 months (mean 43.4 months) previously, A comprehensive method based on Long's matrix formalism and the vech operator of Harris, in addition to the nearest equivalent sphere and cylinder, was used to analyze the refractive data. Results: The mean preoperative refraction in the post-cataract eyes was -4.79 + 1.17 x 0.2 and in the fellow eyes, +0.02 +0.31 x 166. Twelve months after PARK, the postoperative refraction in the post-cataract eyes was-0.90 +0.65 x 2, a significant reduction (P = .15). This postoperative refraction was not significantly different from that in the fellow eye (P = . 93). The pretreatment mean uncorrected visual acuity was 0.12. It improved to 0.41 at 12 months, at which time 52% of eyes achieved a visual acuity of 0.5 or better without correction. All patients regained binocularity, Al 12 months, 2 eyes (11%) showed clinically unacceptable regression; 1 eye with grade 2 haze lost 1 line of corrected visual acuity. Conclusions: Photoastigmatic refractive keratectomy reduced post-cataract myopic ani isometropia, allowing restoration of binocularity in all patients. Overall, the results in this elderly population with previous ocular surgery, posterior capsule thickening, and macular degeneration are not as satisfactory as those obtained from similar treatment of physiological myopia. Stability and postoperative complications are:acceptable. (C) 2000 ASCRS and ESCRS.