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F. Jonasson, B. Sander, T.M. Jørgensen; Photoreceptors Are Affected Before the Retinal Pigment Epithelium in Helicoid Peripapillary Chorioretinal Degeneration (HPCD) . Invest. Ophthalmol. Vis. Sci. 2005;46(13):557.
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Purpose: To locate the earliest changes in the retina and/or the choroid in helicoid peripapillary chorioretinal degeneration (HPCD)/Sveinsson's chorioretinal atrophy (SCRA), using ocular coherence tomography (OCT). Methods: We used stereo fundus photographs, intravenous fluorescein angiography, microperimetry and genetic analysis (TEAD1 mutation), to establish the presence of HPCD/SCRA in two patients. The patients were 37 and 44 years old with visual acuity 20/20 in each eye and 20/40 in the right eye and 20/100 in the left eye, respectively. In both instances macula was involved to some extent. We used OCT–scans (Stratus 3 – Carl Zeiss, Meditec), images, obtained with 512 points per 6mm line scan. The scan was repeated approximately 15 times and processed off–line with an averaging algorithm to reduce laser speckle (noise). For detailed examination the images were shown in gray and color scale, with some emphasis on the border of apparently healthy and apparently diseased area. Results: Following the boarders of healthy and diseased tissue in the macular area: There was an increased thickness of the moderately backscattering outer plexiform layer and a decreased signal intensity from the photoreceptors layers, ie. a decreased signal from the external limiting membrane, and from the inner segment/outer segment junction of the photoreceptors progressing to a total loss of the normally very intense reflection of this last tissue. This was constantly shown in OCT scans from all four eyes.Moving nasally towards and into atrophic region, the intensity of backscatter from the choroidea was increased – indicating a decrease of the absorption of the retinal pigment epithelium (RPE). The OCT detected intensity of the outer RPE did not decrease in comparison to the intensity of nearby healthy regions. In the scar/atrophic region, the neuroretina was highly backscattering, probably due to disorganized tissue and a window defect was present in the retinal pigment epithelium. Conclusions: Contrary to current believes the earliest changes observed are in the sensory retina and not in the retinal pigment epithelium.
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