Effect of varying the optical zone diameter on the results of hyperopic laser in situ keratomileusis

To compare the predictability and safety of laser in situ keratomileusis (LASIK) for low to moderate spherical hyperopia using different ablation zone diameters. Retrospective, nonrandomized, comparative trial. Forty-nine eyes that underwent hyperopic LASIK. Two surgeons (JMD, RKM) performed hyperopic LASIK using the VISX STAR S2 excimer laser (VISX, Inc., Sunnyvale, CA) and the Bausch & Lomb Hansatome microkeratome (Chiron Vision, Irvine, CA) using ablation zone diameters of 5 × 9 mm, 5.5 × 8.5 mm, or 6 × 9 mm (the first number represents the optical zone diameter and the second number represents the diameter of the outer border of the ablation zone). Refractive and visual outcomes at 3 to 6 months after surgery were analyzed. Groups were compared for deviations from targeted spherical equivalent, uncorrected visual acuity, and loss of best spectacle-corrected visual acuity (BSCVA). The mean intended hyperopic correction was +2.48 ± 1.13 diopters (D; 0.63–5.50 D). There were 16 eyes in the 5 × 9-mm group, 15 eyes in the 5.5 × 8.5-mm group, and 18 eyes in the 6 × 9-mm group. On average, the 5 × 9-mm group achieved 97% of the programmed correction, the 5.5 × 8.5-mm group achieved 104%, and the 6 × 9-mm group achieved 112% of the programmed correction. The tendency toward overcorrection in the 6 × 9-mm group compared with the 5 × 9-mm group was statistically significant ( P < 0.05). The incidence of one line loss of BSCVA was greatest in the 5 × 9-mm group (19%) and lowest in the 6 × 9-mm group (6%). These differences were not statistically significant. No eyes experienced a loss of two or more lines of BSCVA at last examination. Hyperopic LASIK using the VISX STAR is safe and effective using different ablation zone diameters. There appears to be an increased tendency toward overcorrection with progressively larger optical zone diameters.