TOPOGRAPHICAL ANALYSIS OF ABLATION CENTRATION AFTER EXCIMER-LASER PHOTOREFRACTIVE KERATECTOMY AND LASER IN-SITU KERATOMILEUSIS FOR HIGH MYOPIA

Purpose: To evaluate the ablation centration after photorefractive ker atectomy (PRK) and laser in situ keratomileusis (LASIK) for high myopi a and to assess the association between decentration and best correcte d visual acuity (BCVA), glare, monocular diplopia, and halo phenomenon . Setting: Mater Private Hospital, Dublin, Ireland. Methods: Corneal t opography was used to analyze centration in two groups of patients wit h myopia of more than 6.0 diopters: 18 had PRK and 18, LASIK. A standa rdized questionnaire assessed the preoperative and postoperative preva lence of glare, monocular diplopia, and halo phenomenon. Results: ''Si gnificant'' ablation decentration (0.5 mm) in the LASlK group (1.33 mm ) was almost twice that in the PRK group (0.75 mm). Glare increased fr om 27% preoperatively to 42% in the PRK group; monocular diplopia incr eased in the LASIK group. Halo phenomenon decreased after both procedu res. Conclusion: Laser in situ keratomileusis represents a step forwar d in the surgical correction of high myopia, but the accuracy of the c orneal ablation location must be improved. Suction ring fixation of th e globe or real time tracking systems may help improve centration.