Optical coherence tomography angiography analysis of macular flow density in glaucoma

Modifications in ocular blood flow may play a significant role in glaucoma development. Optical coherence tomography angiography (OCT-A) is based on the detection and analysis of the reflection behaviour of motion in a static environment and therefore is able to quantify the retinal flow density. We used this new technology to examine the density of the active flow vasculature in the macular area in glaucoma patients compared to healthy patients.

Thirty patients with primary open-angle glaucoma (mean age: 72.6 ± 7.1 years) and 21 healthy patients (mean age: 70.3 ± 8.6 years) were recruited. Patients received perimetry and OCT measurements of the peripapillary retinal nerve fibre layer thickness (RNFLT) and macular retinal thickness and OCT-A of the macular area in the superficial and deep retinal (DR) plexus. Flow density of the OCT-A scan was calculated by binarisation and quantification of the pixel density.

Macular flow density was globally and nasally reduced in glaucoma patients in the superficial (globally: p = 0.0203; nasally: p = 0.0003) and DR plexus (globally: p = 0.0113, nasally: p < 0.0001). There was no significant difference between the superficial retina and the DR concerning the flow density. Flow density showed no significant correlation with perimetry results, RNFLT or retinal segment thickness.

Patients with glaucoma exhibit a reduced macular flow density measured by OCT-A compared to controls. The independence of the macular flow density of the retinal segment thickness changes could indicate an altered vascular element in patients with glaucoma.