LASER IN-SITU KERATOMILEUSIS TO CORRECT HIGH MYOPIA

Purpose: To evaluate the effectiveness, predictability, and safety of laser in situ keratomileusis (LASIK) in 143 eyes with myopia from 8.00 to 20.00 diopters (D). Setting: Alicante Institute of Ophthalmology, University of Alicante School of Medicine, Alicante, Spain. Methods: T his prospective study comprised 143 eyes (94 patients) that had LASIK with the Chiron Automated Corneal Shaper and the VISX 20/20 excimer la ser using a multizone profile and a sutureless hinged corneal flap tec hnique. Results: Uncorrected visual acuity was 20/40 or better in 45.0 % of eyes 3 months postoperatively and in 46.4% at 6 months. Best corr ected visual acuity (BCVA) improved by 0.07 at 3 and 6 months and was stable after 3 months. Mean spherical equivalent was -13.19 diopters ( D) +/- 2.89 (SD) preoperatively and +0.51 +/- 1.63 D at 3 months and 0.18 +/- 1.66 D at 6 months postoperatively. At 3 months, spherical eq uivalent was within 1.00 D of emmetropia in 57.5% of all eyes, 71.0% o f eyes with a baseline refraction from -8.00 to -11.99 D (n = 59), 44. 4% with a baseline refraction from -12.00 to -15.99 D (n = 54), and 53 .0% of eyes with a baseline refraction from -16.00 to -20.00 D (n = 30 ). The respective 6 month percentages were 60.0, 72.4, 46.0, and 50.0% . The regression of effect was similar in all groups (approximately 0. 50 D) between 1 and 3 months, although the high myopia group had furth er regression. Significant corneal steepening and an increase in corne al thickness occurred between 1 and 3 months. Flap thickness was alway s less than predicted with both the 130 and 160 mu m plates, and achie ved laser ablation was deeper than programmed. The relationships betwe en postoperative refraction and preoperative keratometry and postopera tive refraction and the difference in achieved versus programmed ablat ion were significant. Complications at 6 months included epithelial in growth, corneal flap melting, decentered ablation, and irregular astig matism with loss of BCVA, although none was vision threatening. Conclu sion: In this study, LASIK was effective and predictable in the correc tion of high myopia but was more accurate for myopia up to 12.00 D. Cu rrent surgical algorithms must be modified to improve predictability i n higher corrections. Longer follow-up is necessary to evaluate long-t erm incidence of vision-threatening complications.