Peripapillary retinal nerve fiber layer (RNFL) vascular microcirculation in glaucoma using optical coherence tomography-based microangiography (OMAG)

Abstract

Purpose : To investigate the vascular microcirculation changes in peripapillary RNFL in normal, glaucoma suspects (GS), and open angle glaucoma (OAG) subjects using OMAG.

Methods : One eye from each subject was scanned using a montage scanning protocol with a 68 kHz Cirrus HD-OCT 5000 based OMAG prototype system (Zeiss, Dublin, CA) covering a 6.7x6.7 mm² area centered at the optic nerve head (ONH) with a 9.8 µm sampling resolution. Blood flow signals were extracted using a complex OCT signal based OMAG method. Peripapillary RNFL was segmented by a proprietary semi-automatic segmentation program. RNFL vascular en face images were generated using blood flow signals with the highest flow intensity along the axial direction within the RNFL. RNFL vascular microcirculation was measured by calculating the overall blood flux and vessel density within an annulus region centered at the ONH excluding the big retinal vessels (2.5-mm and 3.7-mm as inner and outer diameters, Figure) and compared among groups. Blood flux was defined as the averaged flow signal intensity in the vessels; vessel density measured the percentage of the detected vessels and capillaries within the annulus region, and was defined as the ratio between areas of vessels and the annulus. One-way ANOVA and t-tests were used for statistical analysis. P<0.05 and <0.0167 were considered as statistically significant among three groups, and between each two groups after Bonferroni correction.

Results : Seventeen eyes from 17 normal, 27 eyes from 27 GS, and 42 eyes from 42 OAG subjects were recruited. The mean age and RNFL thickness for normal, GS, and OAG groups were 68.8±11.5, 67.7±7.3, and 65.7±10.7 years (p=0.49), and 94.3±12.4, 88.1±8.4, and 69.8±9.8 µm, respectively (p<0.0001). Significant differences in RNFL thickness were detected between normal and OAG, and GS and OAG, but not between normal and GS (p=0.06). RNFL microcirculation measured as blood flux was significantly lower in OAG and GS compared to normal eyes (p≤0.0015). Significant differences in vessel density were detected between normal and OAG, and GS and OAG, but not between normal and GS eyes (p=0.58) (Figure).

Conclusions : Peripapillary RNFL perfusion detected by OMAG showed significant differences among normal, GS, and OAG subjects. RNFL microcirculation measurement using OMAG may provide useful information for detection of glaucoma.

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