TREATMENT OF MYOPIC ASTIGMATISM WITH THE SUMMIT-APEX-PLUS EXCIMER-LASER

Purpose: To assess the results of surface sequential toric photorefrac tive keratectomy (PRK) with the Summit Apex Plus excimer laser using a n erodible mask.Methods: A prospective study was performed on consecut ive eyes having surface sequential toric PRK over a 4 month treatment period. Attempted astigmatism correction varied from 70 to 100%, depen ding on the power and axis of the cylinder. The myopic correction was adjusted so the combined treatment aim was emmetropia. Refraction, man ual keratometry, corneal haze, and visual acuity data from preoperativ e and follow-up visits over 12 months were divided into various groups based on the preoperative refraction and analyzed. Results: Fifty-nin e eyes from 48 patients had sequential toxic PRK. Preoperatively, the mean spherical equivalent at glasses plane (SEGP) was -4.88 diopters ( D) +/- 3.20 (SD) and the mean refractive cylinder, 2.02 +/- 1.04 D. Th e mean attempted cylinder correction was 1.87 D. At 12 months the mean SEGP was -0.02 +/- 0.67 D, which was not statistically significant fr om piano. The mean refractive cylinder was 0.84 +/- 0.84 D, which was statistically significantly different from zero cylinder power. There was a statistically significant correlation between the preoperative a nd the 12 month postoperative refractive cylinder powers. At 12 months , 34 of 43 eyes (79.1%) had an uncorrected visual acuity of 6/12 or be tter. While 2 eyes in one patient (4.7%) lost two lines of best correc ted visual acuity, with a final acuity of 6/12 in each, no patient los t more than two lines. Conclusion: The manifest refraction cylinder po wer is not fully corrected with the current treatment algorithms; howe ver, surface sequential toric PRK using an erodible mask is capable of treating compound myopic astigmatism with moderate success.