Optic disc perfusion in glaucoma with optical microangiography (OMAG)

Abstract

 

Purpose

 

To investigate the optic disc perfusion differences in glaucomatous and normal eyes using Cirrus 5000 HD-OCT based OMAG.

 

Methods

 

Eyes of normal and glaucoma subjects were scanned with a 67 kHz Cirrus 5000 HD-OCT based OMAG prototype system (Zeiss, Dublin, CA; 245x245 raster cube scan over a 2.4x2.4mm² area centered at the optic nerve head (ONH) region). Microvascular images were generated from the OCT dataset by a proprietary phase compensation method. Two layers were segmented in the ONH region on the microvascular images using proprietary semi-automatic segmentation software: pre-lamina layer (from the inner limiting membrane (ILM) to the anterior surface of the lamina cribrosa (LC)) and LC (between the anterior surface of LC and the outer boundary of choroid). OMAG enface images for pre-lamina layer, LC, and the entire ONH (from ILM to the outer boundary of choroid) were generated using maximum projection. The optic disc margin was defined using Bruch’s membrane opening and was manually delineated on the structural enface image. Optic disc perfusion was measured by calculating the mean flow intensity within the optic disc. Repeated measures analyses were performed to compare optic disc perfusion between glaucomatous and normal eyes and accounted for cluster effect of including both eyes from the same subject. P<0.05 was considered as statistically significant.

 

Results

 

25 eyes from 13 glaucoma subjects (mean visual field mean deviation -4.43±5.19 dB) and 15 eyes from 8 age-matched normal subjects were recruited. There was no significant difference in age between normal and glaucoma subjects (normal vs glaucoma: 59.0±6.6 vs 70.9±3.7 yrs, p=0.11, t-test). Normal eyes had statistically significantly thicker retinal nerve fiber layer thickness compared to glaucomatous eyes (normal vs glaucoma: 85.1±13.2 vs 72.1±10.4 µm, p=0.03, t-test). Optic disc perfusion was statistically significantly lower in glaucomatous eyes compared to normal eyes in pre-lamina layer (normal vs glaucoma: 0.29±0.03 vs 0.26±0.03, p=0.024) and the entire ONH (0.30±0.03 vs 0.27±0.03, p=0.022) but not in LC (0.17±0.02 vs 0.17±0.03, p=0.79) (Figure). The quantification value of LC may be susceptible to the limited light penetration into deep tissue.

 

Conclusions

 

Optic disc perfusion detected by OMAG was significantly lower in glaucomatous eyes than normal controls. Optic disc perfusion measurement may enable detection and monitoring of glaucoma.