LASER IN-SITU KERATOMILEUSIS TO CORRECT MYOPIA OF -6.00 TO -29.00 DIOPTERS

BACKGROUND: Photorefractive keratectomy can cause corneal scarring and visual loss in highly myopic eyes. We evaluated laser in situ keratom ileusis (LASIK) because it has the theoretical advantage of preserving both the corneal epithelium and Bowman's layer. METHODS: In a prospec tive study, LASIK was performed in 62 myopic eyes (42 patients) using the Automatic Corneal Shaper (Chiron Vision) and the Keracor 116 excim er laser (Chiron Technolas). We measured refraction and visual acuity, and evaluated corneal topography (TMS 1) and corneal clarity after 4 to 8 weeks and 4 to 6 months. RESULTS: Four- to 6-month follow up was completed in 51 eyes. The mean preoperative spherical equivalent refra ction was -14.80 diopters (D) (range, -6.00 to -29.00 D). Postoperativ ely, the mean deviation from the target refraction was -1.70 D (range, -9.00 to +2.50 D) at 4 to 8 weeks and -1.90 D (range, -9.50 to +2.25 D) at 4 to 6 months. At 4 to 6 months, 19 eyes (37%) were within +/-0. 50 D of the target refraction, 24 (47%) within +/-1.00 D, 33 (65%) wit hin +/-2.00 D, and 40 (78%) within +/-3.00 D. From 4 to 8 weeks to 4 t o 6 months, the mean regression of myopia was -0.20 D (0.50 D or less in 24 eyes [47%], 1.00 D or less in 32 [63%], and 2.00 D or less in 42 [82%]). In six eyes (12%), the stromal interface was not visible, in 38 (74%) it was barely visible, and in seven (14%) it was clearly visi ble. Corneal topography revealed only small variations in clear-zone s ize and dioptric value, demonstrating a very stable correction 4 to 6 months postoperatively. CONCLUSIONS: LASIK may be a safe and effective procedure to correct high myopia. Further research is required to dev elop satisfactory microkeratome technology, effective laser algorithms , and to determine long-term stability of refraction.