OCT Angiography of Macular Ganglion Cell Complex Circulation in Glaucoma

Abstract

Purpose : To detect macular circulation defects in glaucoma using optical coherence tomography (OCT) angiography.

Methods : One eye of each participant was imaged using a 70 kHz 840 nm wavelength spectral OCT system (RTVue-XR, Optovue, Inc) to obtatin a 6x6 mm volumetric angiography scan of the macula. The split-spectrum amplitude decorrelation angiography (SSADA) algorithm was used. A novel algorithm was used to remove flow projection artifact. The retina was segmented into two slabs: ganglion cell complex (GCC) defined as the nerve fiber layer to inner plexiform layer, and inner nuclear layer+outer plexiform layer (INL+OPL). The total retinal circulation was analyzed using a thick slab that included GCC and INL+OPL. An en face angiogram of each slab was obtained by maximum flow (decorrelation value) projection. Vessel density (VD), the percentage area occupied by vessels, was calculated from a 6x6 mm square region, excluding the foveal avascular zone.

Results : The study included 30 glaucoma and 30 age-matched normal participants. In normal eyes, a dense microvascular network in the macula was visible on en face OCT angiograms (Fig. 1A) which was attenuated in glaucomatous eyes (Fig. 1D). In normal participants, the intra-visit repeatability/population variability of GCC VD, INL+OPL VD, and total retinal VD were 1.8%/4.8%, 5.6%/13.7% and 1.3%/2.9% coefficient of variation, respectively. GCC VD in the glaucoma group (62.5% ± 8.7%; mean ± SD) was lower (P<0.001 Mann-Whitney U test) than the normal group (79.4% ± 3.8%). Total retinal VD in the glaucoma group (82.5% ±8.7%) was also significantly lower (P<0.001) than the normal group (91.0% ± 2.7%). INL+OPL VD in the glaucoma group (61.7% ± 10.5%) was not significantly lower (P=0.098) than the normal group (67.0% ± 9.2%). The area under the receiver operating curve for differentiating normal and glaucoma eyes was 0.984, 0.942 and 0.954 for GCC VD, total retinal VD, and GCC thickness, respectively. With specificity fixed at 95%, the sensitivity of GCC VD, total retinal VD and GCC thickness were 90%, 80% and 77%, respectively. GCC VD was highly correlated (r=0.892, P<0.001) with GCC thickness. GCC VD had a higher correlation with average retinal sensitivity over the corresponding VF points (r=0.453, P=0.012) than GCC thickness (r=0.399, P=0.029).

Conclusions : Glaucoma preferentially affects vessel density in the GCC. The GCC vessel density has high diagnostic accuracy in glaucoma.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.