Peripapillary Retinal Nerve Fiber Layer (RNFL) Vascular Microcirculation in Glaucomatous Eyes with Asymmetric Hemifield Visual Field (VF) Loss

Abstract

Purpose : To investigate the relationship between peripapillary RNFL vascular microcirculation and VF loss in glaucomatous eyes with asymmetric hemifield VF loss using optical coherence tomography-based microangiography (OMAG).

Methods : Glaucomatous eyes with mild VF loss (mean deviation (MD) > -6 dB) in one hemifield and moderate/severe VF loss (MD ≤ -6 dB) in the other hemifield were recruited. Eyes were scanned using a montage scanning protocol with a 68 kHz Cirrus HD-OCT 5000 based OMAG prototype system (Zeiss, Dublin, CA) covering a 6.7 x 6.7 mm² area centered at the optic nerve head (ONH) with a 9.8 µm sampling resolution to assess the vascular microcirculation. Blood flow signals were extracted with a complex OCT signal based OMAG method. RNFL vascular en face images were generated by detecting the highest flow intensity along the axial direction within the RNFL. RNFL vascular microcirculation was measured by calculating the blood flux and vessel density within an annulus region excluding the big retinal vessels (2.5-mm as inner diameter and 3.7-mm as outer diameter) centered at the ONH and divided into superior and inferior quadrants (Figure). Blood flux was defined as the averaged flow signal intensity in the vessels; vessel density was the percentage of the detected vessels and capillaries within the annulus region, defined as the ratio between areas of vessels and the annulus quadrant. Paired t-tests were used to analyze the differences in microcirculation between the corresponding mild and moderate/severe hemifields. P<0.05 was considered as statistically significant.

Results : Ten eyes from 10 subjects were enrolled (mean age 61.2±9.6 years old). Significantly lower MD and thinner RNFL thickness (-10.70±3.82 dB and 64.6±12.0 µm) were found in the corresponding moderate/severe glaucomatous hemifield than in the corresponding mild hemifield (-1.47±1.18 dB and 93.2±21.6 µm, respectively, p≤0.0022). Peripapillary RNFL microcirculation in corresponding moderate/severe glaucoma hemifield also showed significantly lower blood flux and vessel density compared to corresponding mild hemifield (p≤0.0225) (Figure).

Conclusions : Peripapillary RNFL microcirculation reduction showed strong correlation with VF loss and RNFL thinning. RNFL microcirculation measurement using OMAG may provide useful information for detection and understanding of glaucoma.

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