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Christine L. Talamini, Ali S. Raza, Elizabeth A. Dale, Jeffrey G. Odel, Vivienne C. Greenstein, Donald C. Hood; A Study of Eyes with Outer Retinal Disease but Normal Appearing FdOCT Scans of the Macula. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2992.
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To evaluate eyes with abnormal visual fields (VFs) and multifocal electroretinograms (mfERG) but normal appearing or inconclusive frequency-domain optical coherence tomography (fdOCT) scans, the thicknesses of the outer retinal layers were measured.
23 eyes (16 patients) with abnormal VFs and mfERG tests, but normal fdOCT scans were included from a larger group, which included another 50 eyes (41 patients) in which the fdOCT was abnormal. Of the 23 eyes, 15 were tested between Oct. 2007 and June 2009, as part of a previous study, while 8 eyes were tested from June 2009 to Nov. 2010. Testing for all patients included 24-2 and/or 10-2 VFs (Zeiss Meditec), mfERG (103 scaled hexagons, Veris, EDI), and fdOCT imaging (OCT 2000, Topcon) with 3D and line scans of the macula (central 10°). All patients had reliable visual fields (indices < 33%) showing macular defects and good quality mfERG and fdOCT results. The mfERG results were classified as abnormal based on decreased amplitudes and/or increased latencies in the region of the abnormal VF. Based on visual inspection, 3 experienced observers graded the fdOCT scans as normal or inconclusive, as opposed to clearly abnormal. Retinal layers of the fdOCT scans were manually segmented with the aid of a computer program and compared to mean thicknesses from 30 controls. The thicknesses of the outer segment plus RPE layer (OS+: Bruch’s membrane to inner-outer segment line), total receptor (REC: Bruch’s membrane to outer plexiform-inner nuclear layer (INL) border), and the INL were measured. Diagnoses for the 23 eyes were also sought.
One or more of the outer retinal layers was significantly thinner in 11 of the 23 eyes. The REC layer was significantly thinner in 10 eyes and OS+ layer in 8. The diagnoses for the 11 eyes were: Stargardts macular dystrophy (2), cone or cone-rod dystrophy (3), and unknown (6). The remaining 12 eyes were diagnosed as: cone dystrophy (4), retinitis pigmentosa (2), local vascular problems (1), and unknown (5).
Quantitative analysis of fdOCT scans demonstrated significant thinning of the outer retina that was not readily apparent on visual inspection in some scans, emphasizing the need for quantitative measures. The absence of significant thinning in other scans suggests that in certain cases functional loss measured by VFs and mfERGs can precede clear structural changes on fdOCT scans. 1. Dale et al (2010) Doc Ophthalmol; 2. Hood DC et al (2009) IOVS.
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