The Umbra and the Penumbra: Longitudinal Effects of Geographic Atrophy in AMD on the Outer Choroid by Imaging Analysis and Histopathological Correlation.

PURPOSE

To quantitate regional changes in the outer choroidal vessels in patients with geographic atrophy (GA) in AMD and to correlate with a histopathological donor sample.

METHODS

We analyzed 35 participants with GA for in vivo analysis and 1 participant with subject for histopathological analysis. Participants underwent three structural optical coherence tomography scans spaced 6 months apart over 1 year. Quantitative measurements of the outer choroidal vessels were performed in three regions: the GA region, a 150-µm-wide border surrounding the GA, and the area beyond the border. Histopathological analysis was performed using europaeus agglutinin lectin-stained choroidal flat-mount images with the focal planes of both the choriocapillaris and the outer choroidal vessels.

RESULTS

In the GA region, the median vessel area was 3390 µm2 (interquartile range [IQR], 2821 µm2) at baseline, 3139 µm2 (IQR, 2888 µm2) at the 6-month visit and 2888 µm2 (IQR, 2617 µm2) at the 12 month visit (P < 0.001). Our cohort was divided into two subgroups based on RPE atrophy development at the GA border at the 6-month visit. This analysis showed that significant choroidal shrinking occurred only in eyes where the GA border progressed to GA at the 6-month follow-up. Histopathological analysis also demonstrated loss of the outer choroidal vessels, which were predominant in the GA region.

CONCLUSIONS

The outer choroidal vessels seem to decrease with time within the area of GA. The outer vessels decrease over time in eyes where the GA progresses. This finding may suggest that these vessels are under a very tight paracrine control.