EXCIMER-LASER PHOTOREFRACTIVE KERATECTOMY AFTER RADIAL KERATOTOMY

BACKGROUND: Correction of residual myopia after radial keratotomy may be attempted with repeated keratotomy surgery, but predictability can be less than satisfactory. Excimer laser photorefractive keratectomy ( PRK) provides an alternative approach to improving the refractive resu lt in these patients. METHODS: Twenty-five eyes of 20 patients at five clinical locations underwent PRK for residual myopia after radial ker atotomy. The number of incisions ranged from 4 to more than 16. Clear zones ranged from 3 mm to 4 mm. Best corrected visual acuity was 20/20 or better in 16 of the 25 eyes, with a range from 20/12 to 20/80. Unc orrected visual acuity was 20/200 or worse in 15 of the 25 eyes, with a range from 20/25 to finger counting. The interval between radial ker atotomy and PRK averaged 33.5 months, with a range from 5 to 96 months . Nineteen eyes had 6 months or more of follow up; 15 had 12 months or more. RESULTS: Corneal haze was maximal 1 month after surgery (mean /- SE, 0.65 +/- 0.09), and declined to 0.35 +/- 0.16 at 12 months. Twe lve months after PRK, mean keratometric readings were 40.19 +/- 0.81 d iopters (D) and mean spherical equivalent refraction was - 1.42 +/- 0. 47 D. Nine (60%) of the 15 eyes with 12 months follow up were within 1 D of emmetropia and 12 (80%) were within 2 D. Eight (53%) of the 15 e yes had uncorrected visual acuities of 20/40 or better. Spectacle-corr ected visual acuity in the eyes with 12 months follow up improved in 4 , did not change in 4, and worsened in 6. CONCLUSIONS: The results of PRK are less predictable in eyes that have previously undergone radial keratotomy, and these eyes respond with more haze after PRK than norm al eyes.