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A. C. Lee, G. C. Hoffmeyer, E. S. Young, R. E. Burns, K. P. Winter, S. S. Stinnett, C. A. Toth, G. J. Jaffe; Effect of OCT Scan Mode on the Detection of Macular Pathology in Eyes With Neovascular AMD. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2157.
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Frequently, multiple optical coherence tomography (OCT) images are obtained to guide the diagnosis and treatment of macular disorders. However, the optimal OCT scanning protocol remains unknown. We compared the difference in neovascular AMD features identified depending on the scan mode used for analysis.
OCT was performed on 342 visits from 197 patients enrolled in a neovascular AMD clinical trial using six radial scans (6mm, 30 degree offset between scans) generated from the Stratus OCT Fast Macular Thickness Map (FMTM) scan mode, and horizontal (7mm, custom -5 degree offset) and vertical (6mm) line scans centered on the fovea. Line scans have greater pixel density, as each is comprised of 512 individual A-scans (compared to 128 in each FMTM radial scan). Each scan was assessed for the presence and characteristics of macular edema (ME), cysts (CYS), subretinal fluid (SRF), vitreomacular interface abnormalities (VMA/ERM), retinal pigment epithelium abnormalities (RPE) and choroidal neovascularization (CNV). Evaluations from two independent masked graders were adjudicated for the final result. The detection frequency for each variable was compared for protocols using radial and/or line scans.
Certified graders reviewing both FMTM mode and linear mode scans identified macular features missed when reviewing only one modality. Notably, in 17% of scan sets, they characterized RPE height on FMTM scans that were not visualized on the two line scans. Graders detected cysts in linear mode, in 11% of horizontal scans and 10% of vertical scans, that were missed in the corresponding scans from FMTM mode. Graders reviewing all 6 FMTM radial scans picked up a greater percentage of pathology than use of any single radial or line scan in either orientation across virtually all features.
The optimal OCT scan protocol will depend on the specific macular pathology of interest. However, it is not sufficient to base clinical management decisions on the evaluation of a single OCT line scan. A scan protocol that includes the six FMTM radial scans and vertical and 5 degree horizontal offset line scans detects clinically relevant pathology more effectively than either scan mode alone.
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