Custom treatment improves overcorrection, night vision

"An important point to be emphasized with these patients is that information from a large area of the cornea needs to be captured with the pupil dilated. For example, capturing a 7-mm area provides very reliable data for a 6.5-mm pupil compared with capturing a 6-mm area," Dr. Salz stated.

At the recent annual meeting of the American Society of Cataract and Refractive Surgery, he reported the results of CustomCornea treatment in five patients who were re-treated after a refractive procedure. Dr. Salz pointed out that in a patient with a 7.5-mm pupil compared with a 6-mm pupil, 75% of the spherical aberration, 46% of the coma, and 44% of other aberrations would be missed with the smaller pupil size.

The five cases In one case the patient underwent LASIK after radial keratotomy (RK) and had high higher-order aberrations. After the RK, the patient was overcorrected and the LASIK achieved a good visual outcome. However, the quality of the night vision was poor. One preoperative map showed extensive high-order aberrations; and a second map showed dramatic improvement. In this case, Dr. Salz cautioned that checking the pupil size is extremely important, because in the first map the pupil size was 9 mm and in the second it was 5 mm. With both maps and the same pupil size of 6.5 mm, there was still a significant improvement.

"It is unfair to make this type of comparison with different pupil sizes, because simply reducing the pupil size can cause the map to look dramatically better," he said.

The second patient had undergone LASIK for myopia with a small ablation diameter (possibly less than 6 mm) and had a great deal of glare, ghosting, and double vision during night driving. His refractive error was about -0.75 D in each eye. Preoperatively, spherical aberration seemed to be the primary problem (aberration about 0.7 in each eye). In the first eye that underwent customized treat-ment, the spherical aberration decreased to 0.3 and the coma decreased slightly 3 months postoperatively. The patient had a dramatic improvement in night vision symptoms. The second eye then was treated and the results were the same.