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Yongdong Zhou, Cornelius E. Regan, Jr., William C. Gordon, Nicolas G. Bazan; The Application of ex vivo Optical Coherence Tomography in A Rat Model of Light Damage. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4999.
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Both conventional histology study and in vivo optical coherence tomography (OCT) have been used to quantify the retinal injury in animal model of light damage. The border of retinal damage area is beyond the in vivo OCT scanning scope. To avoid the time consuming preparation for conventional histology study and to extend the ability of OCT for peripheral retina, we evaluated the ability and accuracy of commercially available OCT instrument (Spectralis HRA+OCT) for ex vivo imaging of retina in a rat model of light damage.
Six Sprague-Dawley rats were dark-adapted for two days and stimulated with bright light (18kLx, 5h). In vivo OCT was performed before the dark-adaptation and seven days after the light exposure. The eight days after the light exposure, rats were sacrificed and their eyes were collected and fixed (2% glutaraldehyde, 2% formaldehyde, 0.1M Sodium cacodylate). The anterior segments of the eye were removed and eye cups were ready for OCT. A 30 diopter aspheric lens was attached to the front of the OCT instrument. Length of the reference pathway was adjusted manually using the "OCT debug window". Ex vivo OCT was performed. The retinal thickness was measured and the retinal thickness map was construced by these OCT data using image analysis software (spectralis 4.0). The retinal flat mounts and sections were studied by conventional histology study. Rod photoreceptors were labeled with wheat germ agglutinin and photoreceptor cell-dropout maps were constructed from retinal flat mounts. The results from histology study were compared with in vivo and ex vivo OCT results.
Ex vivo OCT was successfully performed and high quality images were obtained. The imaging scope was extended to periphery and the border of retinal damage area could be shown on retinal thickness map. The retinal damage areas varied among individuals, but were similar in both eyes of the same rat. The retinal thickness and retinal thickness map were highly correlated to the results from conventional histology study.
The application of ex vivo OCT in light damage studies is a useful approach to quantify the retinal thickness alteration and retinal damage area. It could save the time and work for conventional histology study. The application of OCT in experimental studies could be extended when in vivo OCT has limitation, e.g., imaging scope and optical media opacity of the animal.
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