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Kwame Antwi-Boasiako, Louvenia Carter-Dawson, Ronald S Harwerth, Nimesh Bhikhu Patel; The relationship between GCIPL thickness and RGC content for experimental glaucoma in non-human primates. Invest. Ophthalmol. Vis. Sci. 2016;57(12):871.
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© ARVO (1962-2015); The Authors (2016-present)
The thickness of the ganglion cell/inner plexiform layer (GCIPL) is commonly used as an assessment of retinal ganglion cell (RGC) content in the macula region. In the macaque model of experimental glaucoma, a change in GCIPL thickness occurs early in neuropathy and is linearly related to the circumpapillary retinal nerve fiber layer thickness measures. The purpose of this study was to determine the correspondence between OCT derived GCIPL thickness and RGC content in the non-human primate.
Histological correspondence was determined for the macula regions of the control and treated eyes of two primates (OHT-64, 24-2 MD=-3.07dB, OHT-66, 24-2 MD=-11.67dB) that had undergone unilateral argon laser scaring of the trabecular meshwork to produce experimental glaucoma. At endpoint, the animals were perfusion fixed and retinal tissue from the macula region, corresponding to the central 20x20 degrees, was dissected. Cell nuclei were labeled using DRAQ5 and the flat mounts were imaged. Through-focus 40x confocal images were used to manually count all non-vascular nuclei in each of the fields imaged. Using retinal vascular features, these regions were subsequently montaged and registered to the endpoint GCIPL and scanning laser ophthalmoscope images to determine the relationship between the structural measures.
Based on the histological and in vivo image registration, there was a 4-8% tissue shrinkage with fixation and processing. The peak cell density in the control eyes was ~62,000 cells/mm2, at 3 degrees from the fovea center. Using 0.01 mm2 regions, the relationship between GCIPL thickness and inner retinal cell density was well described by a single function including data from both the healthy and experimental eyes, which was eccentricity dependent (Cell density = -8.4 + 830xGCIPL – 2172xEccentricity, R2 = 0.71, p<0.01).
In non-human primate eyes, the GCIPL is a good surrogate for cell density in the macula region. The relationship is eccentricity dependent, which is important to consider when investigating structure-function correspondence. Additional studies are required to determine the non-RGC cell contribution to GCIPL thickness at varying stages of neuropathy.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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