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Ratheesh Kumar Meleppat, Pengfei Zhang, Edward N. Pugh, Robert J Zawadzki; Investigation of angular reflectivity of mouse retina layers using directional optical coherence tomography system. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5834.
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© ARVO (1962-2015); The Authors (2016-present)
To present our in vivo observations on angular dependence of mouse retina layers reflectivity measured by directional mouse retinal OCT system.To quantify and model differences observed between angular dependent reflectivity in inner and outer retina layers in different mouse strains.
We repeatedly imaged five retinas of Balb/c and C57Bl/6J mice with a custom-built directional OCT system. The directional retinal imaging was achieved by shifting the imaging beam position across the entrance pupil of the mouse eye. Lateral shifting of the entrance pupil position alters the incident directionality of the retinal illumination.For each mouse several cross-sectional images (B-scans) of the same retinal locus with different beam entry positions were acquired.The average A-scans are used to calculate the angle-dependent reflectivity changes of retinal layers of interest. The directional reflectivity of individual layer is quantitatively measured in terms of FWHM of the reflectivity profile.
The higher axial resolution (~ 2.3µm) of the custom-built OCT system enables complete visualization of major retina layers including clearly delineated posterior tips of the rods outer segments (ROST) and Bruch’s Membrane (BrM) in Albino mice.The separation of these layers was not possible by our imaging system in pigmented animals. It is observed that the reflections from the major retinal layers including the Inner Limiting membrane (ILM), External Limiting Membrane (ELM), the inner/outer segment junction (IS/OS), ROSTand BM/RPE are sensitive to illumination angle. In particular, the mouse ILM and ELM is found to be highly sensitive to beam directionality.
The directional reflectivity of the retinal layers depends on the cellular ultrastructure and possibly on cell morphology. We observed that the reflections from the major retinal layers are highly sensitive to directional illumination and their angular reflectivity have Gaussian profile. The lower FWHM of ILM and ELM suggests their specular reflective properties. The FWHM and center of directional reflectivity suggest contribution of wave-guiding properties of photoreceptor layers to the directional reflectance and can possibly allow studies of photoreceptor integrity and alignment in health and disease retinas.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
A.Reflectivity Profiles of different retinal layers B. Normalized profiles C.Directional Images of retina
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