One-year follow-up results of photorefractive keratectomy for low, moderate, and high primary astigmatism

Objective: To study the efficacy of excimer laser photorefractive keratectomy (PRK) for high, moderate, and low degrees of primary myopic astigmatism. Patients and Methods: Ninety-two eyes of 54 patients with different degrees of compound myopic astigmatism underwent PRK. The eyes were divided by degree of refractive astigmatism into three groups-high (-2.75 to -5.0 diopters [D]), moderate(-1.25 to -2.50 D), and low (less than or equal to-1.0 D). Refraction, corneal topography, slit-lamp findings, and visual acuity with and without correction were assessed. Results: At 12 months, the mean reduction from the preoperative refractive cylinder was 80.7% in the high astigmatism group, 68.4% in the moderate astigmatism group, and 47.6% in the low astigmatism group. The post-treatment residual cylinder axis remained stable in 23 (38.3%) of 60 eyes and deviated in 37 (61.7%) of 60 eyes. The maximal deviation of the residual cylinder axis was 15 degrees. Of the 89.2% of eyes with low cylinder, 81.8% had moderate cylinder, and 85% of the eyes with high cylinder achieved a final uncorrected visual acuity between 20/20 and 20/35 at 12 months. Conclusions: A statistically significant reduction in the refractive cylinder was found in the high, moderate, and low astigmatism groups. The difference between the mean reduction of the high and moderate cylinders compared with the mean reduction of the low cylinders also was found to be statistically significant. The laser used in this study is an efficient tool for correcting high and moderate astigmatism. However, regarding low astigmatism, it was found to be less effective.