Projection Resolved Optical Coherence Tomography Angiography Visualizes Three Distinct Retinal Plexuses in Diabetic Retinopathy

Abstract

Purpose : To describe features of diabetic retinopathy (DR) in projection resolved optical coherence tomography angiography (OCT-A)

Methods : Using a commercial spectral-domain 70kHz OCT instrument (RTVue-XR, Optovue) and the Split-Spectrum Amplitude-Decorrelation Angiography (SSADA) algorithm, 3x3 mm macular scans were obtained in diabetic and normal study participants. A novel algorithm suppressed projection artifacts that blur the retinal vascular layers. A semi-automated algorithm separated this angiogram into superficial, intermediate, and deep retinal plexuses. En face angiograms of each layer, composite-color-coded inner retinal angiograms, and cross sectional angiograms were examined qualitatively.

Results : 19 normal and 35 DR participants were imaged. Projection-resolved OCT-A showed 3 distinct vascular plexuses in the inner retina. In normal eyes, the intermediate and deep plexuses are capillary networks of uniform density and caliber. The superficial plexus contains large and small vessels in a centripetal branching pattern. In DR eyes, areas of capillary nonperfusion were present in all three plexuses. Areas of nonperfusion detected on individual layers can be missed on combined inner retinal angiogram. Dilated vessels of the deeper plexuses, associated with superficial non-perfusion, can often be seen on fluorescein angiogram (FA).

Conclusions : Projection-resolved OCT-A, by presenting 3 retinal vascular plexuses distinctly, reveals pathologies not previously visible on OCT-A and FA.

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

 

Projection-resolved OCT-A of a normal eye shows 3 distinct plexuses: (A) superficial, in the nerve fiber and ganglion cell layers, (B) intermediate, concentrated between the inner plexiform and inner nuclear layer (INL) and (C) deep, concentrated between the INL and outer plexfiform layer. The plexuses merge at the edge of the foveal avascular zone.

 

In this diabetic eye, incongruent areas of capillary nonperfusion are present in the superficial (A), intermediate (B), and deep (C) plexuses, shown in yellow, blue, and red respectively in composite angiogram (E). The two deeper slabs show greater variance of vessel caliber compared to the normal eyes. The yellow arrows point to an area of nonperfusion in superficial slab not evident on the combined inner retinal OCT-A (D) or FA (F). The blue arrows show a dilated vessel in the deep plexus that is evident on FA.