Patients with mixed astigmatism achieve good results after refractive treatment

Dr. Koch, professor and the Allen, Mosbacher, and Law Chair in Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, reported that 62% of eyes achieved 20/20 or better uncorrected visual acuity (UCVA) and 96% achieved 20/40 or better UCVA.

Baylor College is one of six centers that participated in the U.S. clinical trials for WaveScan-guided LASIK (VISX/AMO) for hyperopic and mixed astigmatism. In March the FDA approved CustomVue treatment for mixed astigmatism for 1 to 5 D of cylinder.

The study included 86 eyes of 44 patients with mixed astigmatism. The mean age was 41 ± 11 years. Mean sphere was –1.68 ± 1.12 D (range, –0.50 to –3.0 D), and mean cylinder was +2.98 ± 1.20 D (range, 1.25 to 5.0 D). The MRSE was –0.19 ± 0.89 D (range, –0.75 to 1.25 D).

"As we expect with mixed astigmatism, the patients' vision was basically plano in terms of the spherical equivalent," he said.

"Eighty-six percent of these patients saw 20/25, which is extraordinary. Ninety-six percent saw 20/40 or better," he reported.

Dr. Koch noted that the future iris registration feature on the VISX wavefront system, which is currently only available internationally, will help this mixed astigmatism cohort especially.

"For these patients I look forward to being able to use the iris registration because I believe that it will make these results even better," he said.

Accuracy of treatment

The accuracy of the sphere correction was impressive. Seventy-seven percent of patients were within 0.5 D of intended correction, and 56% of the patients with cylinder correction were within 0.5 D. In addition, more than 90% of each were within 1 D. For MRSE, 66% were within 0.5 of intended correction, and 86% were within 1 D.