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J. C. Izquierdo, R. J. Zawadzki, A. R. Fuller, S. S. Choi, M. C. Lim, J. S. Werner; Inner Retinal Layer Complex Maps Extracted From Volumetric Fourier-Domain OCT Images in Glaucoma Subjects. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4649. doi: https://doi.org/.
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To evaluate feasibility and applicability of thickness maps of an inner retinal three-layer complex: Nerve Fiber, Ganglion Cell and Inner Plexiform Layers (NFL, GCL, IPL) extracted from volumetric in vivo data sets acquired with high-resolution Fourier-domain OCT (FDOCT) using semi-automated segmentation in normal and glaucoma patients.To compare these segmentations with NFL measurements acquired from Stratus OCT and scanning laser polarimetry (GDx-ECC).
A high resolution (4.5 µm) and high speed (12,000 A-scan/s) Fourier-domain OCT system constructed at UC Davis was used to acquire volumetric data sets of optic nerve head (ONH) and surrounding retinal layers in 23 eyes.These data were processed to correct for eye motion artifacts.The resulting volumes were imported into our custom volumetric visualization and semi automatic Support Vector Machine based segmentation software.Thickness maps of combined NFL-GCL-IPL complex were extracted from the volumetric data and compared with Stratus OCT and GDx-ECC.It is thought that the 3-layer complex is a more reliable measure in eyes with glaucomatous loss.
Of 23 eyes, 5 were excluded due to imaging artifacts leaving 9 normal and 9 glaucomatous eyes.Correlation between FDOCT and Stratus OCT was high for all peripapillary quadrants (I, r=0.8; S, r=0.91; N, r=0.91; T, r=0.68) in glaucomatous eyes.In normal eyes, FDOCT measurements of the 3-layer complex were usually thinner than those from Stratus RNFL alone. In glaucoma subjects, for regions of optic nerve damage, FDOCT measurements were thinner than Stratus in those with early glaucoma and they were equivalent in those with advanced damage. Areas of inferior or superior Humphrey visual field depression from glaucomatous damage were consistent with correlated regions of retinal complex thinning measured by FDOCT. Correlation between FD-OCT and GDX-ECC was strong for superior and inferior peripapillary quadrants (r=0.73, r=0.75 respectively).
FD-OCT measurements of a 3-layer retinal complex correlate strongly with Stratus OCT measurements and with specific regions measured by GDx-ECC. Early results show that Stratus OCT may overestimate RNFL measurements in regions of the retina with minimal glaucomatous damage but further studies are needed to verify this finding.
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