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J. W. Brubaker, S. Joeres, L. A. Kim, S. R. Sadda, A. C. Walsh; Differences in External Limiting Membrane Visualization Between Fourier Domain and Time Domain OCT. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2618.
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© ARVO (1962-2015); The Authors (2016-present)
New Fourier domain OCT (FD-OCT) devices provide high speed, high resolution, cross-sectional visualization of the retina. These advantages have been purported to enhance visualization of fine retinal structures. To study this hypothesis, we compared the extent of visualization of the external limiting membrane (ELM) by 3D FD-OCT versus conventional TD-OCT.
3D-OCT scans (128 B-scans x 512 A-scans) were obtained using a prototype 3D FD-OCT instrument (3D-OCT-1000, Topcon, Japan) in 50 eyes of 28 consecutive patients undergoing traditional high resolution (6 B-scans x 512 A-scans) TD-OCT (StratusOCT, Carl Zeiss Meditec, USA). For each eye, one horizontal B-scan closest to the point of fixation was loaded into Photoshop (ver 7.0, Adobe Inc). Points where the ELM was visible were marked on a separate layer with the pencil tool. Care was taken to place the points in a single line so that they could be counted using the histogram function. These data were converted to percentages by dividing the number of counted pixels by the image width. Datasets from the two devices were compared with the Wilcoxon Matched-Pairs Signed-Ranks test.
On average, the ELM was visible across 39% of TD-OCT B-scans in this cohort (range 3-76%). The ELM was visible across an average of 56% of the 3D-OCT scans (range 5-95%). The difference between these two populations was statistically significant (p<0.00001) and represented an increase in the extent of visualization of 45% (see Figure).
High resolution 3D FD-OCT significantly improves visualization of fine intraretinal structures such as the external limiting membrane.
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