Angiography of Optic Disc Perfusion in Glaucoma with a 70 kHz Spectral OCT

Abstract

 

Purpose

 

To compare optic disc perfusion between normal and glaucoma subjects using a commercially available optical coherence tomography (OCT) system.

 

Methods

 

One eye of each subject was scanned twice by a high-speed (70 kHz) 830 nm wavelength spectrometer-based Fourier-domain OCT system(RTVue-XR, Optovue). The optic disc region was scanned using a 3x3 mm volumetric angiography scan. The split-spectrum amplitude decorrelation angiography (SSADA) algorithm was used to compute 3D angiograms. Horizontal- and vertical-priority scans were registered and merged to obtain one motion-corrected angiogram. The optic disc flow index was defined as the average decorrelation value within the disc on the en face maximum flow projection angiogram. Wilcoxon rank-sum test was used to compare values of the optic disc flow index between glaucoma and normal eyes.

 

Results

 

Fourteen normal and ten glaucoma subjects were included. The optic disc flow index in glaucoma subjects was 0.076 ± 0.014 (mean ± SD), which was significantly less (P=0.003, Wilcoxon rank-sum test) than that of the normal group (0.093 ± 0.010). In normal subjects, a dense microvascular network in the optic disc was visible on the OCT angiogram (Fig. 1C). This network was visibly attenuated in glaucoma patients, and perfusion defects were detected at the superotemporal and inferotemporal edges of the disc (Fig. 1F). The within-visit repeatability of the optic disc flow index in normal and glaucoma subjects was 2.1% and 3.2% CV(coefficient of variation), respectively. The population variation of the flow index was 10.8% CV in the normal group.

 

Conclusions

 

Using the SSADA algorithm, high quality OCT angiogram of the optic disc could be obtained in both normal and glaucoma subjects using a commercially available 70 kHz OCT system. Glaucomatous global reduction in disc perfusion could be measured with good repeatability. Focal perfusion defects could be visualized. OCT angiography may be useful in the clinical evaluation of glaucoma.

 

 

Figure 1. Disc photographs (A, D), OCT en face intensity images (B, E) and angiograms (C, F) of optic discs in representative normal (A-C) and glaucoma subjects (D-F). In (C) & (F) the blue circles are the disc areas. Arrows in (F) show perfusion defects (absence of microvascular network).

 

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 627 optic disc