The application of optical coherence tomography angiography in diabetic retinopathy

Abstract

Purpose: To investigate the parafoveal vessel density in diabetic retinopathy using optical coherence tomography (OCT) angiography (Avanti Angiovue SDOCT (Optovue, Inc. Fremont, CA, USA).

Methods: OCT angiography images were acquired from normal subjects and patients with diabetic retinopathy within a 3x3mm area of the central macula. The flow imaging was based on split-spectrum amplitude decorrelation angiography (SSADA), which can assess the vasculature in distinct layers of the retina. The layers assessed were the superficial retinal vascular plexus, deep retinal vascular plexus, avascular outer retina, and choriocapillaris. Parameters quantified include the area of the foveal avascular zone (FAZ) (mm²), parafoveal vessel density (%), and parafoveal vessel flow to no flow index.

Results: A total of 60 eyes were included; 30 eyes from normal subjects and 30 eyes with DR. A marked difference in parafoveal vessel density was observed between normal (49.1 ± 11.2%) and eyes with diabetic retinopathy (36.1 ± 11.0%) (P = .0001) in the superficial retinal vascular plexus. This was also observed in the deep retinal vascular plexus (Normal: 39.6 ± 14.0% vs diabetic retinopathy: 22.9 ± 10.0%) (P=0.001), and choriocapillaris (Normal: 86.9 ± 9.6% vs diabetic retinopathy: 77.6 ± 13.2%) (P=0.01). The FAZ and parafoveal flow index was significantly different only in the superficial and deep retinal vascular plexi.

Conclusions: OCT angiography has for the first time provided an insight into the characteristics of perfusion in all layers of the retina. Although the FAZ is an established parameter in determining the severity of diabetic retinopathy, we observed that parafoveal vessel density, in the retina and choriocapillaris may be more indicative of disease.