Optical Coherence Tomography Angiography for Evaluation of the Fovea Avascular Zone in Diabetic Retinopathy

Abstract

Purpose : Fundus fluorescein angiography (FFA) is currently the gold standard for the diagnosis of macular ischemia, a known complication of diabetic retinopathy (DR). Optical coherence tomography angiography (OCT-A) is a novel and non-invasive method for imaging of the retinal and choroidal vasculature. In contrast to FFA, OCT-A is able to differentiate between the retinal superficial vascular plexus (SVP) and deep vascular plexus (DVP). The purpose of this study is to evaluate the characteristics of foveal avascular zones (FAZ) captured by OCT-A, with reference to FFA, in patients with DR.

Methods : This is a prospective study involving 22 eyes (11 patients, 8 male) with varying DR severities (5 eyes had no DR; 6 had mild non-proliferative DR (NPDR); 6 had moderate NPDR; 2 had severe NPDR and 3 with proliferative DR). All eyes were imaged using OCT-A (Swept-Source Optical Coherence Tomography Angio™, Topcon Corp, Japan) and FFA (Spectralis® Scanning Laser Angiography, Heidelberg Engineering, Germany) to characterize their FAZ. We compared the FAZ area, maximum horizontal and vertical dimensions, for both superficial vascular plexus (SVP) and deep vascular plexus (DVP), between OCT-A and FFA.

Results : The mean age and HbA1C was 59.9 ± 11.6 years and 8.01 ± 1.65 % respectively. For OCT-A, measurements of FAZ area, horizontal and vertical dimensions were 0.335 ± 0.074 mm², 0.656 ± 0.112 mm and 0.662 ± 0.087 mm at the SVP, and 0.277 ± 0.104 mm², 0.605 ± 0.137 mm and 0.572 ± 0.142 mm at the DVP, respectively. The corresponding values obtained via FFA were 0.271 ± 0.135 mm², 0.574 ± 0.140 mm and 0.561 ± 0.154 mm respectively. On OCTA, FAZ area was significantly larger in the SVP compared to DVP (p = 0.015). Comparing OCT-A to FFA , there were no statistically significantly differences in FAZ measurements comparing the SVP and FFA, mean area (p = 0.073), horizontal diameter (p = 0.1), vertical diameter (p = 0.551); or comparing DVP with FFA, mean area (p = 0.714), horizontal diameter (p = 0.956) and vertical diameter (p = 0.665).

Conclusions : OCT-A is comparable to FFA in regard to its ability to accurately characterize the FAZ. Further studies with larger sample sizes are required to confirm our findings.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.