Swelling of the Human Cornea Revealed by High-Speed, Ultrahigh-Resolution Optical Coherence Tomography

Abstract

Purpose. To evaluate the change in thickness of the anterior, stromal, and posterior corneal laminae in response to hypoxia-induced corneal swelling, by means of ultrahigh-resolution optical coherence tomography (UHR-OCT). Methods. A UHR-OCT system, operating in the 1060-nm range, was used to acquire in vivo cross-sectional images of human cornea with a 3.2 × 10-μm (axial × lateral) resolution in corneal tissue. Corneal edema was induced by inserting a thick, positive-powered, soft contact lens, over which the eye was closed and patched for 3 hours. Tomograms were acquired from eight non–contact-lens wearers. Baseline images were obtained before inducing corneal edema, immediately after removal of the patch and the lens, and then every 15 minutes for ∼2 hours. All images were postprocessed with a segmentation algorithm to identify the laminae visible in the image. The apical thickness of the laminae (epithelium [EPI], epithelial-Bowman's membrane [Ep-BM] complex, stroma, and endothelial-Descemet's membrane [En-DM] complex) were determined at each time interval. Results. There was an interaction between time after removal of the hypoxic stimulus and deswelling of the layers (RM-ANOVA; P < 0.001). The epithelial and stromal thickness reduced significantly with time (P = 0.001; P < 0.001, respectively), whereas the Ep-BM and En-DM complexes did not (P > 0.50). All layers except the En-DM complex exhibited a biphasic pattern of recovery. Conclusions. UHR-OCT showed regional differences in swelling due to hypoxic provocation. On removal of the hypoxic stimulus, the rate of recovery varied between layers, and all layers except the En-DM complex exhibited a biphasic recovery.