Hypotony and corneal edema secondary to patching in normal eyes

Over the past decade investigators have used patching when studying corneal response to eye lid closure. In these studies, corneal edema was thought to be secondary to hypoxia, and the results were used to predict corneal response to contact lens wear. None of these studies have measured or controlled the intraocular pressure (IOP) during eye patching. Reports in the literature indicate that hypotonous and hypertensive events may induce corneal edema. In order to evaluate the IOP and corresponding corneal changes, measurements were made on subjects with patched eyes. Thirty subjects were unilaterally patched and randomized into tight and light patch groups to maintain complete lid closure for 4 h. Measurements of IOP and corneal thickness (CT) were made at baseline and at hourly intervals. The contralateral eye served as the control for each subject. Our results indicate a significant decrease in IOP and a corresponding increase in CT in the tight patched group as compared to the light patch group, and baseline controls. These results suggest that the corneal edema which results from patching of the eye may be due to hypotony, or a combination of factors affecting corneal function, rather than hypoxia.