Photorefractive keratectomy for myopia of more than -10 diopters

Twenty-seven consecutive eyes of 18 patients with myopia of more than -10.00 diopters (D) were treated by photorefractive keratectomy (PRK) using the ExciMed UV200LA excimer laser and a double ablation technique in an attempt to achieve a refraction of plano. The preoperative mean spherical equivalent refraction was -13.32 D (standard deviation 2.54, range -10.25 to -20.50). Preoperative spectacle corrected visual acuity ranged from 6/6 to 6/60 and one eye had had two previous refractive keratotomies. Follow up ranged from 3 to 15 months (mean 8.9). At 6 months after surgery, the mean change in refraction was 11.03 D, from a preoperative mean of -13.32 D to a postoperative mean of -2.29 D. The mean keratometric flattening was 5.83 D, from a preoperative mean of 42.92 D to a postoperative mean of 39.09 D. The reason for this large difference is uncertain. At three months the mean spherical equivalent refraction was +0.07 D (SD 2.94, range -10.50 to +3.25). The 14 eyes that had achieved 12 months follow up had a mean spherical equivalent of -1.91 D (SD 3.87, range -11.00 to +2.50). Seven of these 14 eyes have been reablated for manifest scars in association with regression. All 14 eyes had best spectacle corrected visual acuity at or better than their preoperative level.