Circumpapillary microvascular density as a new feature for the everyday glaucoma practice

Abstract

Purpose : To develop a new methodology to identify glaucoma patients based on circumpapillary microvascular density (cpmVD) as measured by Optical Coherence Tomography Angiography (angio-OCT).

Methods : A random eye of 36 healthy subjects (aged 63 ± 12 years) and 33 glaucoma patients (aged 61 ± 8 years with an average visual field loss of -9.5 ± 6.8 dB) were used to develop a new angio-OCT evaluation technique. Optic disc centred 3x3mm images were collected (Angioplex®, Zeiss Cirrus 5000 HD-OCT). The fovea-disc angle, determined by the line that connects the centre of the optic nerve head (ONH) and the fovea, was used to correct the start of the temporal-superior-nasal-inferior-temporal (TSNIT) profile to a common landmark. An annular area with an inner radius of 1.16mm and outer radius of 1.44mm was chosen as the region of interest (ROI). A third-order median filter was applied after obtaining the averaging of each radial line within the ROI. Hence, the cpmVD was calculated through lower envelope modulation avoiding the influence of the major retinal vessels. The presence of small movement artefacts, variation on optic disc dimensions and vessel crowding were also studied. Lastly, the average intensity was calculated at various spatial locations according to six visual field sectors.

Results : A comparison between two healthy subgroups showed that the method is not biased by the presence of slight movement artefacts, optic disc dimensions and vessel crowding (p>0.05). A significant decrease of the cpmVD was observed in the glaucoma group for all visual field sectors (p<0.001). Moreover, cpmVD in the supero-temporal and inferior sectors was the most discriminative when comparing to the normal group. Lastly, it was also observed that glaucoma contributes to a reduction of cpmVD variability when compared to the healthy group.

Conclusions : The presented technique provides a 360 degree robust overview of the cpmVD. It shows that cpmVD measured by angio-OCT can be used as an efficient imaging feature in everyday glaucoma practice.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Circumpapillary microvascular density of the control (blue) and the glaucoma (red) groups with the respective 95% confidence interval (dashed lines).