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Elliott H Sohn, Li Zhang, Johanna Dijkstal Beebe, Robert F Mullins, Michael David Abramoff; Macular structures affected by drusen microenvironment in eyes with AMD. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3958.
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© ARVO (1962-2015); The Authors (2016-present)
Drusen are an early hallmark sign of AMD but relatively little is known about their surrounding retinal structures in vivo. Histopathologic studies by us show ghost vessels in the choriocapillaris underneath drusen. Moreover there is controversy whether the choroid, RPE, and/or photoreceptors are affected first in AMD, thus elucidating the drusen microenvironment will elaborate our understanding of the mechanisms causing AMD and its progression. We sought to quantify the microenvironment surrounding drusen in Spectral Domain Optical Coherence Tomography (SD-OCT) images in patients with AMD.
69 subjects with AMD underwent 61 line scan protocol with enhanced depth imaging performed on the Heidelberg Spectralis SD-OCT device. Drusen, photoreceptor outer segment length (OSL), Retinal Pigment Epithelium (RPE), and choriocapillaris were segmented automatically using an Iowa Reference Algorithms derived graph-based method. A druse was defined as a group of adjoining A-scans where regional sub-RPE virtual space thickness was greater than mean+2*standard deviations. Local choriocapillaris, outer segment and RPE thicknesses were averaged over the drusen region as well as circular regions of 20-160 microns from the drusen boundary separated by 20 microns intervals.
Mean thickness +/- SD (in microns) for OSL, RPE, and choriocapillaris were 31.2 +/- 7.77, 25.7 +/- 1.17, and 8.46 +/- 0.91, respectively, over/under the drusen. OSL was thinnest under the center of drusen and thickens back to normal around 45 microns outside of drusen. RPE is most thin at the central region of drusen, thickens around the edge of drusen, then reverts to normal thickness around 45 microns outside of drusen. Choriocapillaris is also thinnest at the central region of drusen, thickens around the edge of drusen, then reverts to normal thickness around 70 microns outside of drusen.
Drusen microenvironment can be successfully determined in vivo in eyes with AMD using fully automated methods. Photoreceptors outer segment length, RPE, and choriocapillaris are thin around the central regions of drusen. Abnormalities in choriocapillaris appear to be more widespread compared to RPE and photoreceptors outer segments, suggesting that the choriocapillaris has a critical role in the early pathogenesis of AMD.
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