Photorefractive keratectomy for myopic astigmatism: Phase IIA of the Federal Drug Administration study (12 to 18 months follow-up)

Excimer laser photorefractive keratectomy was performed on eight eyes to investigate toric ablation of naturally occurring compound myopic astigmatism. Follow-up ranged from 12 to 18 months. In each surgical case, the spherical component was reduced. The cylindrical component was reduced or eliminated in seven of eight eyes and remained unchanged in one eye. However, six of eight eyes had some residual astigmatism and three had 0.75 diopters of cylinder or more. In six of eight eyes the change in axis in the postoperative cylinder varied between 5 and 10 degrees of the preoperative cylinder axis. In one eye with an eccentric ablation, the axis changed by 40 degrees. In two eyes with loss of best corrected visual acuity of one line each, from 20/20 to 20/25, irregular astigmatism and subepithelial haze persisted 18 months after treatment. One eye gained a line of best corrected visual acuity from 20/20 to 20/15. Two eyes were overcorrected. Twenty-five percent of patients achieved 20/20 or better uncorrected visual acuity, 62.5% achieved 20/40 or better uncorrected acuity, and 100% achieved 20/50 or better uncorrected acuity. These preliminary results of excimer laser photoastigmatic keratectomy compare favorably with reports of photorefractive keratectomy for myopia alone. There were no adverse reactions to treatment. The procedure was effective although some residual astigmatism was found in most patients.