Purpose
To quantitatively visualize retinal vascular flow in patients with diabetic retinopathy using Optical Coherence Tomography Angiography and a novel perfusion density mapping software.
Methods
OCT volumetric images of the macula were obtained (3mm x 3mm and 6mm x 6mm) at 70 kHz A-scans per second using the Optovue Avanti XR OCT system (Fremont, CA). Prototype software employing the split-spectrum amplitudinal decorrelational algorithm (SSADA) was used to construct SD-OCT angiograms of the macular microvasculature. These images were then skeletonized using Matlab software and processed to create topographic maps of vascular density. Average perfusion density was also calculated for the whole volumetric image.
Results
18 eyes of 10 subjects with nonproliferative diabetic retinopathy, 18 eyes of 9 subjects with proliferative diabetic retinopathy, and 8 eyes of 4 control subjects were imaged. The average perfusion density for the control group was 0.2477 ±0.0639 (3x3) and 0.2702 ±0.1006 (6x6). While the average perfusion density for the NPDR group was significantly reduced at 0.2012 ±0.0694 (3x3) and 0.2474 ±0.1048 (6x6). The PDR group appeared futher reduced at 0.1944 ±0.0692 (3x3) and 0.2402 ±0.1047 (6x6).
Conclusions
Topographic perfusion density mapping based upon OCT angiography provides an easily interpretable quantitative picture of retinal vascular flow. Using these novel perfusion density maps, differences between normals and diabetic eyes at various stages of retinopathy were easily recognizable. The ability to derive quantitative values for average volumetric perfusion may also prove useful for detecting progression and anticipating the need for more aggressive interventions.