Multizone/multipass photorefractive keratectomy: six month results

A multizone/multipass photorefractive keratectomy (MP-PRK) technique was used to treat 315 eyes with the 193 nm VISX 20/20 excimer laser. Algorithms were developed to treat the full range of myopia, including 170 low myopic eyes (-1.0 to -6.0 diopters [D]), 105 moderately myopic eyes (-6.0 to -10.0 D), and 40 highly myopic eyes (-10.0 to -27.0 D). Preoperative mean myopia was -6.69 D; astigmatism equal to or greater than -0.5 D (mean -1.18 D) was present in 193 eyes. At one month postoperatively, most eyes were slightly hyperopic (mean +0.8 D); this regressed to a mean of -0.16 D. At six months, 95.5% of low myopes, 84.8% of moderate myopes, and 59.5% of high myopes were within 1.0 D of emmetropia; 78.4% of high myopes were within 2.0 D of the intended correction. There was no loss of 20/40 best corrected visual acuity (BCVA) at six months; a significant gain in 20/25 BCVA was seen in the moderate and high myopia groups (P < .05). At six months, uncorrected visual acuity was 20/25 in 89.4% of low myopes, 75.0% of moderate myopes, and 25.7% of high myopes. Mean haze value was 0.48 at one month and was not significantly different among the three groups (0.44, 0.52, 0.51, respectively). A control group treated with the one-pass multizone technique had a significantly higher amount of haze: 1.05 (P < .01). The data presented compare favorably with those obtained from other centers. Based on these results, we believe that MP-PRK is a safe, reliable technique to correct most low, moderate, and high myopia.