Choriocapillaris Signal Voids Could Characterize AMD

Choriocapillaris signal void size could be a useful tool for clinicians to evaluate eyes with age-related macular degeneration (AMD), according to the results of a recent study.

Researchers set out to compare the choriocapillaris plexus in the eyes of people with intermediate AMD (iAMD) with or without neovascular AMD (nAMD) in the fellow eye. In order to carry out the investigation, they used optical coherence tomography angiography (OCTA).

A host of factors has been implicated in the pathogenesis of AMD, including oxidative damage, genetic predisposition, inflammation, environmental factors, and aging. However, the researchers noted that “strong evidence” exists that retinal pigment epithelium (RPE) and choriocapillaris (CC) damage can characterize AMD.

OCTA allows clinicians to see the retinal and anterior choroidal vascular circulations, and a pattern of dark regions and granular bright areas has been observed and changes with age or myopia. It’s possible that the dark regions are areas of CC flow and the bright areas may be caused by CC dropout. The researchers point out that OCTA is limited, and that flows below a particular threshold are undetectable. “Considering this, CC flow voids have recently been renamed signal voids,” they wrote.

The study was of a retrospective cohort design, and included individuals who were 50 years of age or older, and who had iAMD in at least 1 eye, and either iAMD or nAMD in the other eye. There were 62 patients included in the study, and of those 22 had iAMD in 1 eye and nAMD in the other; 20 had bilateral iAMD; 20 were healthy controls.

“In this cross-sectional study, we investigated CC features in iAMD eyes. Overall, we found an increased average CC signal void size in iAMD eyes with [nAMD] in the fellow eye,” the authors noted. There are several theories about how microvascular choroidal changes are associated with AMD. The improvement in OCTA technology has allowed for closer study of the retinal and choroidal vasculature.

In the current study, the average signal void size in eyes with iAMD was notably greater than the healthy eyes. In addition, the investigators looked at the percent of nondetectable perused CC area (PNPCA). The authors say that they considered PNPCA rather than the total signal void area in order to account for the differences in the area in the part of the eye they were examining for each individual.

The PNPCA was not significantly different in the 3 groups of the current study. “This apparent discrepancy between PNPCA and signal void size suggests that there is an increase in the CC density in areas outside of the signal voids,” the authors wrote. This finding opens avenues for future studies to investigate the mechanism at play.

The full study can be found in the journal Investigative Ophthalmology and Visual Science.