Authors:

Jay C. Wang MD1, Inês Laíns MD1, Rebecca F. Silverman1, Lucia Sobrin MD, MPH1, Demetrios G. Vavvas MD, PhD1, Joan W. Miller MD1, and John B. Miller MD1

1 – Retina Service, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, 243 Charles Street, Boston, MA 02114.A

Purpose: To compare the visualization of the choriocapillaris and deeper choroidal vessels in normal eyes in en face swept source optical coherence tomography (SS-OCT) versus SS-OCT angiography (SS-OCTA).

Methods: This is a cross-sectional study of consecutive eyes without chorioretinal disease. En face SS-OCT and SS-OCTA images of the choriocapillaris and choroid were assessed for visualization of the vasculature. Choroidal vessel densities (CVD) of the choriocapillaris, inner choroid, mid-choroid, and outer choroid were calculated from binarized en face SS-OCT and SS-OCTA images. Paired t-tests and linear regression were used for statistical analysis.

Results: Twenty-seven eyes of twenty-seven patients were included. There was no statistically significant difference between the CVDs of the mid-choroid assessed with en face SS-OCT versus SS-OCTA (p = 0.21). However, there were statistically significant differences between the CVDs for the choriocapillaris (p < 0.001), inner choroid (p < 0.001), and outer choroid (p = 0.006). Qualitative analysis revealed incomplete visualization of vessels in the inner choroid and exaggeration of vessel lumens in the outer choroid with SS-OCTA.

Conclusions: Visualization of the choriocapillaris is superior with SS-OCTA, but it has numerous limitations that make visualization of deeper choroidal vessels less reliable when compared to en face SS-OCT. It is important to understand such limitations when utilizing these technologies to study the choroidal vasculature in chorioretinal disease. 

Figure 1. Scatterplot of the difference in mid-choroid choroidal vessel density (∆CVD), defined as the CVD as measured by swept source optical coherence tomography angiography (SS-OCTA) minus the CVD as measured by en face swept source optical coherence tomography (SS-OCT) versus choroidal depth of the mid-choroid. There was a statistically significant positive linear relationship (p < 0.001). Two representative examples of SS-OCTA and en face SS-OCT and the resulting binarized images from each extreme in choroidal depth are displayed to illustrate this relationship.

Figure 2. Plot of choroidal vessel density (CVD) as measured by swept source optical coherence tomography angiography (SS-OCTA) and by en face swept source optical coherence tomography (SS-OCT) versus depth below Bruch’s membrane for one representative eye. Binarized images from SS-OCTA and en face SS-OCT of the inner choroid, mid-choroid, and outer choroid are displayed.