Comparison of Visual Functions in Myopia over -6.0 D after PhotorefractiveKeratectomy and Laser in situ Keratomileusis

Overview

1. 41 myopes undergoing PRK and 31 patients undergoing LASIK for correctionof spherical refractive error were examined before and 1, 3, 6 a 12 months aftersurgery on Schwind Multiscan with ablation zone between 5 and 7 mm. Meanpreoperative spherical equivalent of refraction was -8.0 ± 1.7 D in PRK group and-9.2 ± 2.1 D in LASIK one.2. Contrast sensitivity (CS) was tested on a computerized system of the Contrastsensitivity 8010 type in 6 spatial frequencies (0.74; 1.97; 3.69; 7.39; 14.77; 29.55 c/deg)and the best corrected visual acuity (BCVA) was measured on the normalizedcharts with Landolt rings.3. At 12 months postoperatively, mean spherical equivalent of refraction was -0.6± 1.0 D (PRK) and -1.0 ± 0.8 D (LASIK). A refractive error within ± 0.5 D had 31.5%(PRK) and 57.5% (LASIK) patients. Increasing of BCVA was measured in 51.5%(PRK) and 41.9% (LASIK) patients about 1 optotype to 2.5 lines. Mean CS in 6frequencies reached 99.4; 102; 105; 109; 115 and 140%of preoperative values in PRKgroup and only 96; 95.8; 96.3; 95.8; 97.8 and 94.6% in LASIK one. 4. At 12 months after surgery, mean spherical equivalent, CS was better andnumber of patients with increased BCVA was significantly higher after PRK, thanthose attained with LASIK. On the other hand, a number of patients with a refractive error within ± 0.5 D was higher and percentage of reoperations was lower inLASIK group.

Key words:
photorefractive keratectomy, laser in situ keratomileusis, myopia,contrast sensitivity, LogMAR charts