Results of laser in situ keratomileusis in hyperopic compound astigmatism

Abstract

Purpose: To evaluate the efficacy and safety of steepening the flatter meridian with laser in situ keratomileusis (LASIK) to correct hyperopic compound astigmatism using the Schwind-Keratom laser with the MultiScan System and the active tracking system for centering the ablation.

Setting: Instituto Barraquer de América, Bogotá, Colombia.

Methods: From June to December 1997, LASIK was performed in 111 eyes to correct congenital hyperopic compound astigmatism. Preoperatively, the mean spherical equivalent was +2.58 diopters (D) (range +1.50 to +3.50 D) in 37 eyes (low dioptric group), with a mean sphere of +3.66 D (range +1.75 to +5.50 D) and a mean cylinder of -2.11 D (range -0.50 to -5.00 D); +4.71 D (range +3.51 to +6.00 D) in 50 eyes (middle dioptric group), with a mean sphere of +5.58 D (range +4.00 to +7.00 D) and a mean cylinder of -1.83 D (range -0.50 to -4.50 D); and +7.26 D (range +6.01 to +10.00 D) in 24 eyes (high dioptric group), with a mean sphere of +8.25 D (range +6.50 to +10.00 D) and a mean cylinder of -1.98 D (range -0.50 to -4.00 D) in 24 eyes. Postoperative results were measured at 10 days and 6 months.

Results: At 6 months, the mean residual subjective spherical defect was +0.32 D (range -0.50 to +1.00 D) in the low dioptric group, with a mean cylinder of -0.61 D (range 0.00 to -1.75 D); all eyes were within +/- 1.00 D of emmetropia. The mean defect was +0.82 D (range 0.00 to +2.50 D) in the middle dioptric group, with a mean cylinder of -0.61 D (range 0.00 to -2.50 D); 80% of eyes were within +/- 1.00 D of emmetropia. The mean defect was +1.10 D (range -0.50 to +3.00 D) in the high dioptric group, with a mean cylinder of -1.39 D (range 0.00 to -3.25 D); 77% of eyes were within +/- 1.00 D of emmetropia. In the study group as a whole, 90% of eyes had a cylinder correction within +/- 1.00 D of emmetropia. Uncorrected visual acuity (UCVA) was 0.50 (20/40) or better in 23.4% of eyes preoperatively and 0.50 (20/40) or better in 71.0% 6 months postoperatively.

Conclusions: Steepening the flatter meridian with the MultiScan System safely and effectively corrected hyperopic astigmatism. The rapid recovery of UCVA was due not only to correction of the ametropia, but also to the centering provided by the active tracking system.