Computerized Scheimpflug densitometry as a measure of corneal optical density after excimer laser refractive surgery in myopic eyes

Abstract

Purpose: To evaluate changes in anterior corneal optical density and the refractive index after photorefractive keratectomy (PRK) using a rotating Scheimpflug system.

Setting: Department of Ophthalmology, University Federico II, Naples, Italy.

Design: Comparative case series.

Methods: Anterior corneal optical density was evaluated with a rotating Scheimpflug system at baseline and 3 months and 12 months after PRK in eyes with a refractive error between -6.00 diopters (D) and -12.00 D (study group). A control group of unoperated eyes with the same refraction range was used to calculate corneal optical density and the Gladstone-Dale constant in unoperated eyes using the Gladstone-Dale formula. In the study group, changes in the anterior corneal optical density were evaluated over time and variations in the anterior corneal refractive index were obtained using the Gladstone-Dale constant.

Results: The study group comprised 37 eyes and the control group, 200 eyes. In the study group, the mean anterior corneal optical density and refractive index, respectively, were 27.71 ± 4.39 and 1.360 ± 0.05 at baseline, 37.812 ± 12.31 and 1.491 ± 0.16 after 3 months (P<.001 compared with baseline), and 26.29 ± 4.93 and 1.341 ± 0.06 after 12 months (P=.03 compared with baseline). The mean corneal optical density in the control group was 27.71 ± 4.31 (SD), and the resultant Gladstone-Dale constant was 0.013.

Conclusion: An early increase and a subsequent reduction in anterior corneal optical density and the refractive index were present in myopic eyes during 1 year after PRK.