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David M. Wu, Humberto Ruiz, SriniVas Sadda; Photoreceptor Loss At The Margins Of Geographic Atrophy Lesions. Invest. Ophthalmol. Vis. Sci. 2011;52(14):123.
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Geographic atrophy is responsible for severe visual loss in approximately one out of every five patients with age-related macular degeneration (AMD). With several new treatments for non-exudative AMD now in development, it has become important to better understand the pathophysiology of geographic atrophy and the junctional zone. In particular, it would be useful to determine whether there are areas within the geographic atrophy lesion that have not yet suffered irreversible damage.
Spectral-domain optical coherence tomography (SD-OCT) images were obtained from 9 eyes of 9 patients with geographic atrophy. Thirty-seven individual B-scans from each eye were then analyzed in 3D-OCTOR grading software and manual segmentation of the retinal pigment epithelium (RPE) and photoreceptor outer segments (POS) were performed to generate area and defect maps of these structures.
The mean area of the RPE defect was found to be 2.00 mm2 (SD ±1.70) whereas the mean area of the photoreceptor outer segment loss was found to be 2.11 mm2. (SD ±1.83). These areas were not found to be significantly different by paired t-test (p=0.08). Interestingly, projection maps of RPE atrophy and photoreceptor loss did not always show perfect overlap. Whereas in most cases, the boundaries of photoreceptor loss coincided with or slightly exceeded the patch of RPE atrophy, occasional areas of intact photoreceptors within zones of atrophy could be identified.
Although areas of geographic atrophy of the RPE show considerable overlap with areas of photoreceptors loss, some margins of the atrophic lesion show photoreceptor loss beyond the area of the RPE defect whereas other margins show photoreceptor survival in areas devoid of RPE. Further study is necessary, as emerging therapies may allow rescue of these persisting photoreceptors within geographic atrophy lesions.
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