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W. Anderson, G. Gregori, D. L. Budenz; Total Retinal Thickness Defects on Spectral Domain Optical Coherence Tomography Are Correlated With Glaucomatous Visual Field Abnormalities. Invest. Ophthalmol. Vis. Sci. 2007;48(13):496.
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© ARVO (1962-2015); The Authors (2016-present)
Peri-papillary total retinal thickness (PPTRT) maps can reduce the very large volume datasets produced by spectral domain optical coherence tomography (SD OCT) to reliable, reproducible and characteristic representations of structure which may have pathologic significance for glaucoma. This study investigated the relationship between asymmetry of defects in retinal thickness and visual field abnormalities.
SD OCT was used to raster scan a 6 x 6 x 2 mm volume centered on the optic disc in 37 eyes of 21 glaucoma clinic patients and 56 eyes of 29 normal subjects. Automated segmentation of the internal limiting membrane (ILM) and anterior retinal pigment epithelium (RPE) boundaries generated total retinal thickness (TRT) measurements. Pattern thickness defects on 2-D pictorial colormaps were subjectively interpreted after training based on images of normal subjects. In addition, quantitative PPTRT asymmetry was numerically evaluated by comparing differences above and below the disc between corresponding regions determined from the pattern of mean normals. SD OCT TRT pictorial pattern and quantitative hemifield asymmetry were compared to glaucoma hemifield test (GHT) results from contemporaneous 24-2 SITA-standard threshold strategy standard automated perimetry (SAP).
Among glaucoma clinic patients there were 16 eyes with reliable SAP GHT outside normal limits (ONL) and 21 eyes with GHT either within normal limits (18) or borderline (3). Qualitative assessment of pattern thickness defects correctly predicted GHT ONL with 81% specificity and 81% sensitivity. A threshold difference of greater than 20 µm on the quantitative PPTRT hemifield test yielded 60% sensitivity and 95% specificity for an SAP GHT result of ONL. In 5 of 6 eyes with a false negative quantitative PPTRT hemifield test, global retinal thinning (corresponding to median mean deviation of -18 dB on SAP) caused failure of the quantitative asymmetry detection algorithm.
SD OCT structural measures employing PPTRT analysis are correlated with a perimetric parameter of functional abnormality in glaucoma patients. TRT methodology capitalizes on the reliable and reproducible performance of automated segmentation when applied to the favorably high reflectance contrast on OCT at the ILM and RPE retinal interfaces. With further refinement, SD OCT PPTRT hemifield quantitative analysis may prove useful in documenting early structural changes of clinical significance for diagnosis of glaucoma and progression.
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