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N. Hutchings, A. A. Moayed, S. Hariri, C. Hyun, T. L. Simpson, K. Bizheva; Anisotropic Swelling of the Human Cornea Revealed by High Speed, Ultrahigh Resolution Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3673.
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© ARVO (1962-2015); The Authors (2016-present)
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).
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.
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.
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.
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