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Rithambara Ramachandran, Xian Zhang, Kirsten G. Locke, Vivienne C. Greenstein, David G. Birch, Donald C. Hood; The Intensity of Outer Retinal Layers Seen on Frequency Domain OCT in Patients with Outer Retinal Disease. Invest. Ophthalmol. Vis. Sci. 2012;53(14):811.
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On frequency domain optical coherence tomography (fdOCT) scans, the inner segment ellipsoid (ISe) band (aka inner segment/outer segment border)  is present , but less intense  in patients with achromatopsia and cone dystrophy. Here we examine the intensity of 5 retinal layers/bands in both reasonably healthy regions (with ISe band) and in severely affected regions (without ISe band) of patients with outer retinal disease.
Horizontal line scans through the fovea of 30 healthy controls, 11 patients with Stargardt disease (STGD), 8 with retinitis pigmentosa (RP), 7 with achromatopsia (ACHM), 7 with choroideremia (CHM), and 7 with age-related macular degeneration (AMD) were obtained with fdOCT (Spectralis, Heidelberg). All patients showed regions with and without ISe preservation. Two bands [ISe band and outer limiting membrane (OLM)] and 3 layers [outer nuclear layer (ONL), inner nuclear (IN) layer and retinal ganglion cell layer plus inner plexiform layer (RGC+)] were segmented with a computer-aided manual procedure . The ISe and the OLM bands were divided into segments 3 pixels (11.7 υm) in depth and 10 pixels (60.1 υm) in width. The 3 layers were divided into segments 10 pixels wide. The relative intensity of each segment was determined by dividing the segment’s average intensity by the average intensity of a local region ±45 pixels wide and extending from the RNFL/RGC border to Bruch’s membrane.
When the ISe was present, the patient’s mean relative ISe intensity was typically within the normal 95% CI limits for all disease groups except for ACHM. In addition, for all diseases, the relative intensities of the RGC+ and IN layers were within normal limits whether or not the ISe was present. In contrast, the ONL intensities were typically above normal limits when the ISe was absent [STGD: 11/11 (11 of 11 patients), RP: 8/8, ACHM: 5/7, CHM: 7/7, AMD: 6/7], and within normal limits when the ISe was present (STGD: 7/11 RP: 8/8, ACHM: 5/7, CHM: 7/7, AMD: 7/7). In all ACHM and AMD patients, the OLM was more intense in regions where the ISe was absent, but within normal limits in regions with an ISe.
The intensity of outer retinal layers can be less than (e.g. ISe) or greater than (e.g. OLM, ONL) normal in patients with outer retinal disease. Further, the intensity can depend upon whether the region is severely affected (ISe absent) or not (ISe present). In some cases, the variations in ONL intensity appeared to be due to pigment migration and/or a splitting of the outer plexiform layer, while the reason for the greater intensity of the OLM is not clear. 1. Spaide & Curcio. Retina 2011. 2. Birch DG, Wen et al. IOVS 2011. 3. Hood DC, Zhang et al. IOVS 2011. 4. Hood DC, Lin et al. IOVS 2009.
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