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Ketki Soin, Justin Wanek, Thasarat S Vajaranant, Mahnaz Shahidi; Mapping of Thickness and Reflectivity of Individual Retinal Layers in Primary Open-Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4522.
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© ARVO (1962-2015); The Authors (2016-present)
Primary open-angle glaucoma (POAG) affects the inner retina. Alteration in the outer retina in eyes with POAG are not well characterized. We measured retinal layer thickness and reflectivity and determined if there were changes in the outer retina in eyes with mild vs. advanced POAG.
Spectral domain optical coherence tomography (SDOCT) was performed in 10 eyes of 9 glaucoma subjects (age, 53 + 19 years). Eyes were categorized into mild (MD > -6 dB) or advanced (MD < -6 dB) glaucoma groups based on perimetry. Five eyes had mild (MD -1.75 + 0.78 dB) and 5 eyes had severe glaucoma (MD -22.30 + 6.39 dB). SDOCT image volumes consisting of 61 horizontal raster B-Scans were obtained, encompassing a 30°x25° field centered on the fovea. A automated image analysis algorithm was applied to the SDOCT image volume for detection of retinal layer boundaries and generation of enface maps of: 1) nerve fiber layer (NFL), ganglion cell and inner plexiform layers (GCIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), outer segment complex (OSC = photoreceptor outer segment and retinal pigment epithelium (RPE)), and total retina (TR) thickness, and 2) NFL, photoreceptor inner ellipsoid (ISe), and RPE intensity. Mean thickness and intensity values were calculated in 8 of 9 macular ETDRS subfields (excluding central subfield). General linear model multivariate analysis was performed to determine the effects of glaucoma stage and macular location on thickness and reflectivity of retinal layers.
NFL, GCIPL, and TR thickness measurements as well as NFL intensity and the ratio of ISe to RPE were significantly lower in subjects with advanced glaucoma (P < 0.001). There were no significant differences in INL, OPL and ONL thickness (P > 0.11). OSC thickness was lower (P = 0.003) and ISe intensity was lower (P=0.006) in subjects with advanced glaucoma. RPE intensity was similar between glaucoma groups (P = 0.83). The thickness of all evaluated retinal layers and NFL intensity were significantly different among macular subfields (P < 0.001). ISe and RPE intensity measurements were similar among macular subfields (P > 0.83).
Reduced OSC thickness and ISe intensity suggests structural changes to the outer retina in eyes with advanced POAG. Mapping of thickness and reflectivity of retinal layers is promising to provide a new approach to monitor glaucoma damage.
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