Meeting News CoveragePerspective

OCT angiography with projection resolution algorithm quantifies retinal vessel density

COLORADO SPRINGS, Colo. — Using OCT angiography and a novel “projection resolution and reflectance compensation” algorithm to remove artifact and signal effects, David Huang, MD, PhD, and colleagues found that glaucoma preferentially affects vessel density in the ganglion cell complex more than in deeper layers, according to a study presented at the American Ophthalmological Society meeting here.

“This year I want to talk about studying the macula in the context of glaucoma,” Huang said. “Our technology has moved ahead so that our algorithm is a little bit different now. OCT angiography is great. At first you’re amazed at the information you have, but then you are bothered by the many artifacts. ... [O]ur effort now is getting rid of these artifacts.”

David Huang

Huang said the most important artifact in this context is the projection artifact, which represents moving blood cells in the superficial retina that produce shadows that are interpreted as flow, impeding the ability to visualize deeper layers of the retina. As well, signal artifact affects calculation of vessel density.

Huang and colleagues applied the compensation algorithms and used OCT angiography (AngioVue, Optovue) to study 30 eyes of 30 patients with perimetric glaucoma; 10 had mild disease, 15 had moderate disease, and five had advanced disease. Thirty age-matched controls were also studied.

In the superficial plexus, there was a statistically significant decrease of 22% in vessel density between the control group and the glaucoma group (P < .001). In the intermediate and deep layers, vessel density was decreased by 8% and 13%, respectively.

“Glaucoma does affect vessel density in all three plexuses, mostly in the superficial plexus,” Huang said.

Huang and colleagues also found that reflectance compensation improves reliability of vessel density measurement, macular retinal perfusion can be quantified with high repeatability, and superficial vessel density has high diagnostic accuracy and is well correlated with glaucoma severity as measured by visual field. – by Patricia Nale, ELS

Reference:

Huang D. Angiography of macular circulation in glaucoma. Presented at: American Ophthalmological Society; May 19-22, 2016; Colorado Springs, Colo.

Disclosure: Huang reports financial interest in OCT and OCT angiography technology with Optovue and previously with Carl Zeiss Meditec.

COLORADO SPRINGS, Colo. — Using OCT angiography and a novel “projection resolution and reflectance compensation” algorithm to remove artifact and signal effects, David Huang, MD, PhD, and colleagues found that glaucoma preferentially affects vessel density in the ganglion cell complex more than in deeper layers, according to a study presented at the American Ophthalmological Society meeting here.

“This year I want to talk about studying the macula in the context of glaucoma,” Huang said. “Our technology has moved ahead so that our algorithm is a little bit different now. OCT angiography is great. At first you’re amazed at the information you have, but then you are bothered by the many artifacts. ... [O]ur effort now is getting rid of these artifacts.”

David Huang

Huang said the most important artifact in this context is the projection artifact, which represents moving blood cells in the superficial retina that produce shadows that are interpreted as flow, impeding the ability to visualize deeper layers of the retina. As well, signal artifact affects calculation of vessel density.

Huang and colleagues applied the compensation algorithms and used OCT angiography (AngioVue, Optovue) to study 30 eyes of 30 patients with perimetric glaucoma; 10 had mild disease, 15 had moderate disease, and five had advanced disease. Thirty age-matched controls were also studied.

In the superficial plexus, there was a statistically significant decrease of 22% in vessel density between the control group and the glaucoma group (P < .001). In the intermediate and deep layers, vessel density was decreased by 8% and 13%, respectively.

“Glaucoma does affect vessel density in all three plexuses, mostly in the superficial plexus,” Huang said.

Huang and colleagues also found that reflectance compensation improves reliability of vessel density measurement, macular retinal perfusion can be quantified with high repeatability, and superficial vessel density has high diagnostic accuracy and is well correlated with glaucoma severity as measured by visual field. – by Patricia Nale, ELS

Reference:

Huang D. Angiography of macular circulation in glaucoma. Presented at: American Ophthalmological Society; May 19-22, 2016; Colorado Springs, Colo.

Disclosure: Huang reports financial interest in OCT and OCT angiography technology with Optovue and previously with Carl Zeiss Meditec.

    Perspective
    Joel S. Schuman

    Joel S. Schuman

    This was an important study and a novel analysis with new findings. Dr. Huang convincingly demonstrates that there is correspondence of the OCT angiography ganglion cell complex vascularity with visual field sensitivity. In other words, you have a diminution of vascularity in areas that correspond to poorer visual sensitivity. The measurements are highly reproducible as he showed. He differentiates between the GCC and the outer nuclear layer/outer plexiform layer. He also differentiates between total retina vascularity and its relationship with glaucoma, which is important, as well as the spatial correspondence between the GCC vascularity and visual field performance.

    There are some limitations to this study. It is a small study, it is cross-sectional, and glaucoma severity distribution is skewed to moderate to severe.

    The OCTA technology has some limitations itself: Acquisition speed has an effect on the vasculature identified, and the vasculature that is seen with OCTA may be present but not perfused, which cannot be discriminated with the OCTA technique.

    Is this a better way to detect glaucoma? It will take further investigation in a large cohort of patients. It will be especially interesting for evaluation in early glaucoma detection. The potential for longitudinal assessment awaits further exploration.

    • Joel S. Schuman, MD
    • OSN Glaucoma Board Member

    Disclosures: Schuman reports he receives royalties for intellectual property related to OCT owned by Massachusetts Institute of Technology and Massachusetts Eye and Ear Infirmary and licensed to Carl Zeiss Meditec.

    See more from American Ophthalmological Society Meeting