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E. J. Knott, Y. Zhou, K. G. Sheets, W. C. Gordon, N. G. Bazan; Photoreceptor Loss in the Light Damaged Mouse Retina: Evaluation by Ocular Coherence Tomography and Histological Sections. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1398.
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Retinal degenerative diseases involve loss of photoreceptor cells and vision impairments. Intense light initiates damage that leads to photoreceptor apoptotic cell death in albino rodents. In the past, measurements of photoreceptor loss depended on histology and therefore required many time points and extensive numbers of animals. The purpose of this study was to determine if photoreceptor cell loss in light-induced retinal degeneration in mice could be accurately characterized by Optical Coherence Tomography (OCT) (Spectralis, Heidelberg Engineering).
Balb/c mice (25g) were acclimated for 7 days, anesthetized and imaged via OCT. Following 2 days recovery from anesthesia, eyes were dilated and mice stimulated with bright light (4 kLx, 0h, 2h, 4.5h, and 6.5h). After recovery in 8 h of dark, followed by normal cycled light for 10 days, mice were imaged again with OCT. Eyes were then collected and high resolution plastic sections obtained from which the outer nuclear layer (ONL) thickness could be measured. OCT photoreceptor integrity was measured manually using Heidelberg Engineering software. Histological sections of eyes were measured optically using a filar-micrometer, calibrated against a Pyser-Sgi stage micrometer. OCT and histological measurements were compared at 100 µm increments along the superior-inferior meridian through the optic nerve.
Pre-light damaged and untreated control animals exhibited a consistent photoreceptor thickness (~115 µm) as measured by OCT and from optical sections. Following various times of light exposure and 10 days of recovery, animals displayed a decline in the photoreceptor layer. Plotted retinal ONL profiles from both methods were similar, and ratio plots of time-matched optical section/OCT section retinas demonstrated little to no difference.
Experimental retinal degenerative studies usually are evaluated by analysis of histological sections at different time points, thus removing each animal from the experimental population. Our results show that OCT imaging of retinas can be used to achieve measurements of photoreceptor layer thickness that are comparable to those obtained from optical analysis of light microscopy. This indicates that a single animal can be accurately and repeatedly imaged by OCT throughout an experiment. Therefore, OCT is a reliable tool to evaluate time-relevant changes in retina.
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