PHOTOASTIGMATIC KERATECTOMY FOR CORRECTION OF ASTIGMATISM IN CORNEAL GRAFTS

The efficacy and safety of excimer laser photoastigmatic refractive ke ratectomy (PARK) for treatment of astigmatism after penetrating kerato plasty (PKP) was evaluated in this study. Methods. A VisX 20/20 excime r laser was used to correct the regular astigmatic component of the gr afts. The epithelium was removed manually in seven cases and in three patients with the PTK mode of the laser. The results were analyzed for uncorrected visual acuity (UCVA), best corrected acuity (BCVA), haze, and changes in the cylinder and axis. The vectorial change in astigma tism was measured using Alpins' method. Results, Preoperative astigmat ism ranged from 3.50 to 11.25 D (mean, 5.98 +/- 2.28) and the mean att empted correction of astigmatism was 6.28 +/- 1.56 D (range, 3.50-9.00 D). The induced reduction of net corneal astigmatism was 48.1%. The v ector-corrected astigmatism, which was 6.40 +/- 3.49 D at 1 month post operatively, was reduced at 12 months to 4.28 +/- 2.42 D. The Alpin Su ccess Index varied in the range 0.06 to 1.0. Although the UCVA improve d by greater than or equal to 2 lines in 60% of the eyes, the BCVA dec reased in 40% of the eyes and three patients required a reoperation. C onclusion. Although PARK is relatively safe and effective in reducing post-PKP cylinder and improves UCVA, the frequently and surprisingly l ate-developing corneal haze often impairs the BCVA.