Optic nerve head perfusion in normal eyes and eyes with glaucoma using optical coherence tomography-based microangiography

Abstract

Background: To investigate the differences of perfusion in the optic nerve head (ONH) between normal and glaucomatous eyes using optical microangiography (OMAG) based optical coherence tomography (OCT) angiography technique.

Methods: One eye from each subject was scanned with a 68 kHz Cirrus 5000 HD-OCT-based OMAG prototype system centered at the ONH (Carl Zeiss Meditec Inc, Dublin, CA, USA). Microvascular images were generated from the OMAG dataset by detecting the differences in OCT signal between consecutive B-scans. The pre-laminar layer (preLC) was isolated by a semi-automatic segmentation program. En face OMAG images for preLC were generated using signals with highest blood flow signal intensity. ONH perfusion was quantified as flux, vessel area density, and normalized flux within the ONH. Standard t-tests were performed to analyze the ONH perfusion differences between normal and glaucomatous eyes. Linear regression models were constructed to analyze the correlation between ONH perfusion and other clinical measurements.

Results: Twenty normal and 21 glaucoma subjects were enrolled. Glaucomatous eyes had significantly lower ONH perfusion in preLC in all three perfusion metrics compared to normal eyes (P≤0.0003). Significant correlations between ONH perfusion and disease severity as well as structural changes were detected in glaucomatous eyes (P≤0.012).

Conclusions: ONH perfusion detected by OMAG showed significant differences between glaucoma and normal controls and was significantly correlated with disease severity and structural defects in glaucomatous eyes. ONH perfusion measurement using OMAG may provide useful information for detection and monitoring of glaucoma.

Keywords: Optical coherence tomography angiography; optic nerve head perfusion; optical microangiography (OMAG); primary open-angle glaucoma (POAG).

Figure 1

Example of retinal layer segmentation. Two retinal boundaries were segmented: inner limiting membrane (ILM) (the yellow line), retinal pigment epithelium (RPE) (the red line outside the optic disc) and anterior surface of lamina cribrosa (LC) (the same red line within the optic disc). (A,B) Structural and blood flow cross-sectional image superimposed with segmented retinal boundaries.

Figure 2

An example result of the vascular en face image of pre-laminar tissue (preLC) of a normal (A-D) and a glaucomatous eyes (E-H). (A,E) Show the structural en face images; (B,F) display the cross-sectional structural images sampled at the horizontal red lines in (A) and (E) superimposed with blood flow signals from preLC, and vertical yellow dashed lines indicate the optic disc margin by detecting the end of Brush’s membrane; (C,G) are the vascular en face images from preLC; (D,H) present the detected blood vessel maps from preLC.

Figure 3

Scatter plots for three optic nerve head perfusion metrics and clinical measurements [visual field median deviation (MD) and pattern standard deviation (PSD)] and structural biometrics [retinal nerve fiber layer (RNFL) thickness, cup-to-disc ratio (CDR), and rim area]. R² with P values in the parentheses are presented, where R_N² and R_G² indicate R² value for normal and glaucomatous eyes, respectively.