LASIK affects epithelial thickness, not stromal thickness

ROCHESTER, Minn. — The central corneal epithelium is thicker in the first year after LASIK than before LASIK, according to a small study using confocal microscopy. There was no significant change in flap thickness or central stromal thickness from 1 month to 12 months after LASIK in the study.

The study, performed here at the Mayo Clinic, confirmed earlier reports that LASIK flaps are “much thinner than expected.” The researchers used a Bausch & Lomb Hansatome microkeratome with an intended flap thickness of 180 µm, but the resulting flaps were measured at a mean 160 µm.

The researchers studied 18 eyes of 12 patients who received LASIK with a planned 180 µm flap to correct refractive errors from -2 D to -11 D. The patients’ corneas were examined before LASIK and at 1 week and 1, 3, 6 and 12 months postoperatively using in vivo confocal microscopy.

Before LASIK, the mean epithelial thickness was 46 µm. This increased 22%, to 56 µm, at 1 month postop (P = .001). The study authors attributed the increase to epithelial hyperplasia. After the 1-month mark, epithelial thickness did not change, but remained thicker at 12 months after LASIK (mean 54 µm) than before LASIK. Total mean flap thickness at the 1-month follow-up was 160 µm and did not change thereafter. Total stromal thickness changes throughout the follow-up period were not significant.

The study is published in the August issue of Ophthalmology.