title: Comprehensive method of analyzing the results of photoastigmatic refractive keratectomy for the treatment of post-cataract myopic anisometropia.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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. At 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 anisometropia, 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.
authors.affiliation: St. Paul's Eye Unit, Royal Liverpool University Hospital, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Patterson
authors.forename: S B
authors.initials: SB
authors.lastname: Kaye
authors.forename: N P
authors.initials: NP
authors.lastname: O'Donnell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015858:Anisometropia / Q000209:etiology / Q000601:surgery*; D002387:Cataract Extraction / Q000009:adverse effects*; D003315:Cornea / Q000601:surgery*; D005260:Female; D006801:Humans; D054018:Lasers, Excimer; D019654:Lens Implantation, Intraocular / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000209:etiology / Q000601:surgery*; D018903:Photorefractive Keratectomy; D012029:Refraction, Ocular; D012086:Reoperation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016896:Treatment Outcome; D015348:Vision, Binocular; D014792:Visual Acuity