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  • Title: Effect of varying the optical zone diameter on the results of hyperopic laser in situ keratomileusis.
    Author: Davidorf JM, Eghbali F, Onclinx T, Maloney RK.
    Journal: Ophthalmology; 2001 Jul; 108(7):1261-5. PubMed ID: 11425684.
    Abstract:
    PURPOSE: To compare the predictability and safety of laser in situ keratomileusis (LASIK) for low to moderate spherical hyperopia using different ablation zone diameters. DESIGN: Retrospective, nonrandomized, comparative trial. PARTICIPANTS: Forty-nine eyes that underwent hyperopic LASIK. INTERVENTION: 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 x 9 mm, 5.5 x 8.5 mm, or 6 x 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). MAIN OUTCOME MEASURES: 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). RESULTS: The mean intended hyperopic correction was +2.48 +/- 1.13 diopters (D; 0.63-5.50 D). There were 16 eyes in the 5 x 9-mm group, 15 eyes in the 5.5 x 8.5-mm group, and 18 eyes in the 6 x 9-mm group. On average, the 5 x 9-mm group achieved 97% of the programmed correction, the 5.5 x 8.5-mm group achieved 104%, and the 6 x 9-mm group achieved 112% of the programmed correction. The tendency toward overcorrection in the 6 x 9-mm group compared with the 5 x 9-mm group was statistically significant (P < 0.05). The incidence of one line loss of BSCVA was greatest in the 5 x 9-mm group (19%) and lowest in the 6 x 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. CONCLUSIONS: 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.
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