RELATION OF VISUAL SYMPTOMS TO TOPOGRAPHIC ABLATION ZONE DECENTRATIONAFTER EXCIMER-LASER PHOTOREFRACTIVE KERATECTOMY

Background: The authors used computer-assisted videokeratoscopy to ana lyze the relation of photorefractive keratectomy ablation zone decentr ation to subjective patient assessments of disturbing visual symptoms. Methods: Ablation zone decentration was measured 1 month postoperativ ely. The study population was divided into two groups: group 1, patien ts whose ablation zone decentrations were less than 0.50 mm; group 2, patients whose ablation zone decentrations were greater than 0.50 mm. Visual symptoms including glare, rings or halos around lights and prob lems with night driving were scored preoperatively and 6 months postop eratively. The Hotelling T-square and chi-square tests were used. Resu lts: The mean decentration from the center of the ablation zone to the pupillary center was 0.30 mm and 190 degrees for group 1 compared wit h 0.66 mm and 198 degrees for group 2. The Hotelling T-square test sho wed a significant statistical preoperative/postoperative difference in group 1 (P < 0.03) for the halo symptom category. No other symptom ca tegory showed a significant statistical difference in either group for the mean scores. The Hotelling T-square test did not show a statistic ally significant difference between the two groups preoperatively to p ostoperatively regarding the mean scores of the individual patient dif ferences for the three symptoms. The only significant statistical diff erence for the individual patient ratings preoperatively to postoperat ively was for the halo symptom category (chi-square = 7.756; P < 0.03) . Conclusions: Multivariate analysis did not show a significant statis tical difference preoperatively between the two groups or postoperativ ely except for group 1 with regard to the halo symptom category. It ap pears from this study that ablation zone decentrations less than 0.89 mm from the pupillary center do not necessarily produce unwanted visua l symptoms 6 months postoperatively.