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F. Knezevich, R. Zeimer, S. Vitale, Y. Ding, C. Marks, H. Quigley, D.S. Friedman, N. Congdon, H. Jampel; Image Analysis to Obtain Macular Retinal Thickness Summary Parameters for Characterizing Glaucomatous Ganglion Cell Loss: The GILS (Glaucoma Imaging Longitudinal Study) . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3367.
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Purpose: The Glaucoma Imaging Longitudinal Study (GILS) was designed to evaluate the utility of two imaging modalities (optic disc and macula) in characterizing glaucomatous nerve tissue loss. A major effort has been to develop new retinal thickness (RT) summary parameters in the macular region to reflect the anatomy of the retinal ganglion cell and nerve fibers of the macular area and the contours of tissue loss believed to occur in glaucoma. Methods: Patients (aged 35-91 y (mean, 69 y), 51% female, 19% African-American) with primary open-angle glaucoma, confirmed by at least 2 visual fields with glaucoma hemifield test "Outside normal limits" or MD <5% or PSD <5%, with corroborating optic disc abnormalities, were enrolled in the GILS. Baseline RT measurements were obtained with the Retinal Thickness Analyzer (Talia Technologies, Ltd, Neve Ilan, Israel). An automated algorithm was used to compute an RT map. Image analysis was used to compute differences from normative RT values and to isolate the "ganglion cell region" (GCR) associated with the course of the nerve fiber layers in the macula (also corresponding to the thickest layer of ganglion cells, i.e., the area subserving the central visual field) by using a masking region to trim areas > 2200 µm from the foveal center and to trim the circular area (radius 1000 µm) centered on the foveola (this region is generally spared until end-stage glaucoma). Within the GCR, RT summary parameters were computed in 75 eyes for the superior and inferior hemispheres and their nasal and temporal quadrants as follows: median RT loss, 90th percentile of RT losses and % area with ≥1 SD of RT loss. Results: Conclusions: Glaucomatous damage is reflected in parameters of RT loss in the posterior pole, as significant portions of the GCR showed losses, some as deep as 80% of the120-µm GCR thickness. These findings indicate that RT measurements at the posterior pole hold promise as a new indicator for glaucomatous damage. RT summary parameters (microns, mean (SD)). Losses are deviations from normal RT values View OriginalDownload SlideView OriginalDownload Slide
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