Comparison of optical zones in hyperopic laser in situ keratomileusis: 5.9 mm versus smaller optical zones.

摘要

PURPOSE: To compare the results of hyperopic laser in situ keratomileusis (LASIK) with a 5.9 mm optical zone (OZ) with those with smaller zones (4.4 to 5.5 mm). SETTING: Instituto de la Vision, Buenos Aires, Argentina. METHODS: The results of LASIK with a 5.9 mm OZ (147 cases) were compared with those in a previously reported group treated with OZs of 4.4 to 5.5 mm (679 cases). In the 5.9 mm group, 31.3% (46 eyes) had low hyperopia, 46.9% (69 eyes) had moderate hyperopia, and 21.8% (32 eyes) had high hyperopia. In the smaller OZ group, follow-up was 1 month in 79.4% (539 eyes), 3 months in 75.5% (501 eyes), 6 months in 68.5% (465 eyes), and 1 year in 38.3% (260 eyes). The hyperopic population studied was divided into 3 subgroups based on the preoperative spherical equivalents of the manifest refraction: subgroup A, low hyperopia: < or = +2.0 diopters (D); subgroup B, moderate hyperopia: +2.0 to +3.0 D; and subgroup C, high hyperopia: > +3.0 D. The following parameters were measured postoperatively: uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), refraction (evolution and distribution), and visual acuity lines gained and lost. RESULTS:The preoperative mean spherical equivalents in the 5.9 mm OZ group were +1.47 +/- 0.41 (SD) (subgroup A); +2.98 +/- 0.41 (subgroup B); and +5.13 +/- 0.61 (subgroup C). In the smaller OZ group, they were +1.31 +/- 0.74, +2.56 +/- 0.28, and +5.28 +/- 0. 69, respectively. At 12 months, the distribution of eyes in the 5.9 mm OZ group with refractions within +/-1.0 D were as follows: subgroup A, 100%; subgroup B, 100%; and subgroup C, 94.2%. In the smaller OZ group, the distributions were 100%, 95.3%, and 71.4%. In the 5.9 mm and the smaller OZ groups, the UCVA was 20/40 or better in 92.0% and 81.8% of eyes, respectively, in subgroup A; 94.6% and 100%, respectively, in subgroup B; and 76.5% and 77.9%, respectively, in subgroup C. The percentage of eyes with 0 +/- 1 line of BCVA 12 months after the procedure was also determined in the 5.9 mm OZ group and compared with the percentages in the smaller OZ group. CONCLUSION: Results of hyperopic LASIK with a 5.9 mm OZ in eyes with low, moderate, and high hyperopia are more stable, predictable, and safe than those in eyes with OZs smaller than 5.9 mm.