Foveal avascular zone acircularity index in diabetic eyes and healthy controls measured by optical coherence tomography angiography (OCTA)

Abstract

Purpose : Foveal avascular zone (FAZ) acircularity index, a metric that does not require the axial length correction for retinal magnification, was used to compare differences between diabetic eyes and healthy controls.

Methods : 3x3mm OCTA images centered at the fovea were obtained in 20 control subjects (20 eyes, mean age 49, range 32-65 years) and 47 diabetic subjects (47 eyes, mean age 51, range 21-69 years) using a spectral domain OCT system (Avanti RTVue-XR, Optovue, Fremont, CA). A split-spectrum amplitude decorrelation angiography (SSADA) algorithm was used to generate en face OCT angiograms (Fig A & B). Diabetics were divided into 3 groups based on the stage of disease: no clinically observable diabetic retinopathy (NoDR), nonproliferative diabetic retinopathy (NPDR), or proliferative diabetic retinopathy (PDR). Full-thickness angiographic images (superficial + deep capillary plexuses) were analyzed by manually tracing the FAZ. FAZ acircularity index was calculated as the ratio of the perimeter of the FAZ to the perimeter of a circle with equal area. Statistical analysis was performed using unpaired t-tests.

Results : Mean FAZ acircularity index ± SD was 1.39±0.19 in the control group, 1.37±0.11 in the NoDR group, 1.66±0.40 in the NPDR group, and 1.75±0.40 in the PDR group. FAZ acircularity index was significantly higher in the NPDR and PDR groups compared to the NoDR group (p=0.0058 and p=0.0009, respectively) and control group (p=0.0088 and p=0.0013, respectively). No significant difference was detected between the NoDR and control groups.

Conclusions : Acircularity index provides a quantitative evaluation of the FAZ without the need for retinal magnification correction, which may prove clinically useful for detecting and grading diabetic retinopathy.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Figure: Higher FAZ acircularity index in diabetic retinopathy. (A) FAZ acircularity index = 1.12 in healthy control. (B) FAZ acircularity index = 2.49 in patient with nonproliferative diabetic retinopathy. FAZ border is shown in red.