Photoastigmatic keratectomy for correction of astigmatism in corneal grafts

The efficacy and safety of excimer laser photoastigmatic refractive keratectomy (PARK) for treatment of astigmatism after penetrating keratoplasty (PKP) was evaluated in this study. Methods. A VisX 20/20 excimer laser was used to correct the regular astigmatic component of the grafts. 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 astigmatism was measured using Alpins' method. Results, Preoperative astigmatism ranged from 3.50 to 11.25 D (mean, 5.98 +/- 2.28) and the mean attempted 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 vector-corrected astigmatism, which was 6.40 +/- 3.49 D at 1 month postoperatively, was reduced at 12 months to 4.28 +/- 2.42 D. The Alpin Success Index varied in the range 0.06 to 1.0. Although the UCVA improved by greater than or equal to 2 lines in 60% of the eyes, the BCVA decreased in 40% of the eyes and three patients required a reoperation. Conclusion. Although PARK is relatively safe and effective in reducing post-PKP cylinder and improves UCVA, the frequently and surprisingly late-developing corneal haze often impairs the BCVA.