Abstract
Purpose: :
To evaluate the change in thickness of the anterior, stromal and posterior laminae of the cornea in response to hypoxia induced corneal swelling using an ultra-high resolution optical coherence tomographer (UHR-OCT).
Methods: :
The custom, high-speed UHR-OCT system1, operating in the 1060nm range, was used to obtain two dimensional images of the cornea. The device acquires 47,000 A-scans per second and has a resolution in corneal tissue of 3.2µm (axial) and 10µm (lateral). Images were obtained from the right eye of five non-contact lens wearers. Corneal edema was induced by inserting a thick, positive powered soft contact lens over which the eye was closed and patched for 3 hours. Baseline images were obtained prior to inducing corneal edema. Experiment images were obtained immediately after removal of the lens and patch, and every 10 minutes subsequently for up to 2 hours. All images were post-processed with a speckle noise reduction algorithm to improve image contrast2 and tissue boundaries were identified with a semi-automated segmentation algorithm. The apical thickness of the anterior epithelial-Bowman’s membrane complex, stroma, and posterior endothelial-Descemet’s membrane complex was determined.
Results: :
Prior to inducing corneal swelling, the mean thickness for the anterior, stroma, and posterior laminae was 53µm, 480µm and 14µm, respectively. Hypoxia induced swelling resulted in, on average, a 9.2% increase in total corneal thickness. Immediately after lens removal, the thickness of the anterior lamina was unchanged (55µm); the stroma (517µm) and posterior lamina (28µm) were significantly thicker (p<0.05). 60 minutes after lens removal, the laminae thickness had returned to near baseline levels.
Conclusions: :
Alterations in thickness due to hypoxia differ across the axial expanse of the cornea. The thickness of the epithelial-Bowman’s layer complex is unchanged, while both the thickness of the stroma and the endothelial-Descement’s layer complex increases. Swelling of the posterior lamina of the cornea is only visible with ultra-high resolution OCT.1. Puvanathasan et al. (2008) Opt. Letters 33:2479-2481.2. Puvanathasan & Bizheva. (2007) Optics Express 15:15747-15758.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • cornea: clinical science • imaging/image analysis: clinical