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Mahnaz Shahidi, Fatimah Mohammad, Justin Wanek, Jennifer I. Lim, Ruth Zelkha; Enface Outer Retinal Imaging In Age-related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4110.
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Age-related macular degeneration (AMD) is the leading cause of vision loss in older people. In neovascular AMD, choroidal neovascularization leads to outer retinal pathologies, including pigment epithelium detachment (PED) and subretinal fluid (SRF) accumulation. The purpose of this study is to report an automated image feature analysis method applied to enface outer retinal images for detecting pathological changes due to AMD treatment.
Spectral domain optical coherence tomography (SDOCT) was performed in 6 subjects diagnosed with neovascular AMD. Enface outer retinal images of 4 mm by 4 mm retinal areas were generated from high density SDOCT volume scans by extracting and combining image data from a retinal depth coincident with the photoreceptor inner and outer segment junction. Pathologic features (PED and SRF) were automatically segmented from enface outer retinal images after intensity adjustment and thresholding. The area and mean intensity of the segmented pathologic features were calculated. Retinal thickness maps were generated and central subfield thickness (CST) was recorded. The area and intensity of the pathologic features, and CST measurements obtained at baseline and following treatment were compared.
SDOCT cross sectional B-scan images displayed hyper-reflectivity at locations of PED, while hypo-reflectivity was observed at locations with SRF. Accordingly, on enface outer retinal images, PEDs were visualized as regions with higher intensity, while regions corresponding to SRF had lower intensity, as compared to the relatively uniform intensity of the surrounding areas. The area of PED was clearly visualized on enface outer retinal images and quantitatively measured. Adjacent to the PED, regions with reduced intensity were visualized that represented SRF. Subfoveal scarring was clearly delineated on enface outer retinal images and the area remained unchanged between visits. Likewise, there was no change in CST and visual acuity. Following treatment, increased intensity in areas with SRF corresponded with a decrease in CST and improvement in visual acuity. A decrease in the SRF area following treatment was consistent with a decrease in CST and improvement in visual acuity.
Enface outer retinal imaging and quantitative assessment of PED and SRF is of potential value for evaluating disease progression and therapeutic intervention in AMD.
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