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Torcato Santos, Jose G Cunha-Vaz; Automated analysis of retinal extracellular space using Optical Coherence Tomography. A non-invasive indirect identification of the sites of alterations of the Blood-Retinal Barrier. Invest. Ophthalmol. Vis. Sci. 2016;57(12):435.
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© ARVO (1962-2015); The Authors (2016-present)
Monitoring alterations of the Blood-Retinal Barrier (BRB) is presently performed by fluorescein angiography (FA), an invasive method that uses an intravenous injection. We describe a new non-invasive method for localization and quantification of increases in retinal extracellular space, herein designated as OCT-Leakage using either Cirrus HD-OCT or AngioPlex (Carl Zeiss Meditec) devices. Increases in retinal extracellular space are surrogate indicators of breakdown of the BRB.
A semi-automated segmentation algorithm, able to identify 7 retinal layers, was applied to 48 eyes from 48 diabetic patients between 43 and 82 years of age (m±sd: 61.2±8.1 [years]) with normal Retinal Thickness (RT) (n=10), Subclinical Macular Edema (n=30) and Clinical Macular Edema (n=8). We also examined 25 eyes from 21 age matched healthy volunteers between 49 and 75 years of age (m±sd: 60.6±5.4 [years]). Optical reflectivity values were obtained for the full A-Scan within the retina and by retinal layer. The identification of Low Optical Reflectivity (LOR) sites corresponds to an increase of extracellular space. OCT-Leakage maps for full A-Scan within the retina and by retinal layer were thereafter generated to localize sites of increased extracellular space.
Increases in Central Subfield RT in the eyes with subclinical and clinical macular edema were located mainly in the INL and OPL. These increases correlated well with the changes in LOR ratios, r=0.8 and r=0.6 (p<0.01) for INL and OPL, respectively. The OCT-Leakage maps identified well the sites of fluorescein leakage on FA. Furthermore, the location of the increases in extracellular space identified by the LOR ratios could be seen to predominate in different retinal layers in different eyes, indicating well the location of the increase of the extracellular space resulting from the breakdown of the BRB.
The method here described is able to detect and locate non-invasively the sites of leakage, i.e., alteration of the BRB in diabetic eyes. It offers an added value by identifying the changes occurring at different layers of the retina. OCT-Leakage location and quantification is thus able to complement OCT-Microangiography making it more likely to replace FA.
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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