OCT Angiography (OCTA) of Diabetic Retinopathy

Abstract

 

Purpose

 

To non-invasively evaluate the retinal microvasculature in diabetic human subjects with swept-source (SS) and spectral-domain (SD) optical coherence tomography (OCT) angiography.

 

Methods

 

Ten subjects diagnosed with diabetes mellitus were enrolled in a cross-sectional, observational study and all underwent a complete ophthalmic examination. Subjects were evaluated using a high-speed 1050 nm SS-OCT prototype system (100,000 kHz) and a 840 nm SD-OCT prototype system (67,500 kHz). SD-OCT angiography was performed using a 3X3mm and 6X6mm raster scan pattern, which consisted in the transverse scanning direction of, respectively, four consecutive B-scans each comprised of 245 A-scans in the 3X3 raster scan and a pair of consecutive B-scans each comprised of 350 A-scans in the 6X6 raster scan pattern. A total of 245 B-scans positions located 12.4 μm apart over the 3 mm distance and 350 B-scans positions located 17.1 μm apart over the 6 mm distance were sampled. Retinal vasculature was assessed in three retinal slabs consisting of the superficial retina, middle retina and outer retina. The vasculature was reconstructed using an intensity based algorithm and visualized en face for comparison with fluorescein angiograms (FA).

 

Results

 

OCTA in subjects with non-proliferative diabetic retinopathy (DR) or proliferative DR showed areas of non-perfusion, irregular capillaries, and microaneurysms that were qualitatively similar to findings on FA. However, capillary non-perfusion could be localized to either the superficial or middle retina in most cases using OCTA whereas this distinction could not be made with FA. Microaneurysms were observed in OCTA but their number, size and shape did not correspond to FA findings in some cases.

 

Conclusions

 

OCTA generates high-resolution images that are qualitatively similar to retinal vasculature imaged with conventional fluorescein angiography. While OCTA is completely non-invasive and may be performed with greater ease and frequency than conventional fluorescein angiography, some clinical findings, such as vascular leakage, cannot yet be assessed with OCTA. OCTA may serve as an alternative method of assessing retinal vascular changes when conventional fluorescein angiography cannot be performed.  

 

Inner retinal OCTA and FA of the fovea in a subject with severe non-proliferative diabetic retinopathy.

 

 

Inner retinal OCTA and FA of the fovea in a subject with severe non-proliferative diabetic retinopathy.