Correlation of Macular Retinal Thickness Loss with Optic Disc Changes in Eyes with Primary Open-angle Glaucoma: The GILS (Glaucoma Imaging Longitudinal Study)

Abstract

Abstract: : Purpose: Glaucomatous losses of retinal ganglion cell and nerve fiber tissue have been shown to precede glaucomatous visual field changes, hence there is hope that such structural changes may serve as useful early markers to identify those at risk of progression of visual field defects. Although glaucomatous nerve tissue loss is traditionally assessed at the optic disc and peripapillary regions, retinal thickness (RT) losses in the macular region have been documented in glaucoma patients. The Glaucoma Imaging Longitudinal Study (GILS) was designed to evaluate the utility of two imaging approaches, of the optic disc and macula, in evaluating glaucoma status. Methods: Patients with primary open-angle glaucoma, confirmed by at least 2 visual fields with glaucoma hemifield test "Outside normal limits", MD <5%, or PSD <5%, with corroborating optic disc changes, were enrolled into GILS. Optic disc scanning was done with the Heidelberg Retinal Tomograph (HRT II, Heidelberg Engineering GmbH, Heidelberg, Germany). Baseline RT measurements were done with the Retinal Thickness Analyzer (Talia Technologies, Ltd, Neve Ilan, Israel). We studied standard HRT II summary parameters for nerve fiber layer thickness (NF-T), cross-sectional area (NF-A), and rim area in the temporal, inferotemporal, and superotemporal regions of the disc. Summary RT loss parameters (mean (RT-mean), median (RT-M), 90th percentile (RT-90), and area of 1SD thickness loss (RT-1SD)) were derived for the quadrants of the RT map. Pearson correlations (r) of HRT with macular RT parameters were done. Results: Modest associations (r values ranging from 0.25 (p=0.07) to 0.42 (p=0.001)) between HRT inferotemporal NF-T, NF-A, and rim area and the RT parameters of inferotemporal RT-mean, RT-M, RT-90, and RT-1SD were observed. Correlations between HRT parameters of the temporal and superior disc and the RT parameters of corresponding regions of the macula were weak. Conclusions: Within the GILS population at baseline, we did not find striking correlations between RT (macular) and HRT (disc) parameters. This lack of correlation could be explained if changes at the disc and macula in glaucoma do not occur simultaneously. Longitudinal follow-up of the GILS cohort will be necessary to confirm or refute this explanation.

Keywords: clinical (human) or epidemiologic studies: sys • imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • optic disc