Large preoperative pupil size does not predict visual symptoms postLASIK

San Francisco-Large preoperative pupil size does not positively correlate with an increase in visual symptoms after wavefront-guided myopic LASIK, according to the results of a prospective study reported by researchers from Stanford University, Stanford, CA. The relationship between pupil size and quality of vision after LASIK is a source of controversy with various publications reporting different results, said Annie Chan, MD, who is in the residency program at the university’s Department of Ophthalmology.

"We undertook this study to address further this issue," she said.

The study included 51 patients who underwent bilateral surgery for low to moderate myopia. Patients were asked to complete a questionnaire for each eye asking about problems with glare, haze, halos, clarity, and nighttime visual disturbances. The surveys were completed preoperatively and again at 1 week and 1, 3, 6, and 12 months after surgery. In order to identify the effect of pupil size on outcomes, patients were stratified into three groups based on their mesopic pupil size: small (6 mm). Mesopic pupil size and pre- and postoperative variables were evaluated using analysis of variance.

One month after surgery no statistically significant differences were found between groups with regard to any of their visual symptoms, whereas at 12 months, results showed, surprisingly, that patients with small pupils experienced more glare at night than their counterparts with medium or large pupils, Dr. Chan said. At this last visit, no statistically significant differences were found between the three pupil size groups in any of the other symptoms measured, she added.

"In all groups, glare at night had worsened at 1 month after surgery compared with baseline, but then it improved progressively with time," Dr. Chan said. "However, by the last visit, glare symptoms at night were reduced compared with baseline in eyes with medium and large pupils."