Combined depth imaging using optical coherence tomography as a novel imaging technique to visualize vitreoretinal choroidal structures.

Spectral domain optical coherence tomography (SD-OCT) is a noninvasive technique to visualize cross-sectional images of vitreoretinal structures. Image averaging during eye tracking increases the signalto-noise ratio and improves image quality. The point of maximum sensitivity on SD-OCT (known as the “zero-delay line”) is in the vitreous; with increasing depth, the signal is reduced and details of the choroid are reduced. More recently, enhanced depth imaging on spectral domain optical coherence tomography has increased the ability to visualize the choroid, capturing images with the choroid close to the zero-delay line. However, with this modality, details of the posterior vitreous are reduced. A healthy volunteer was scanned with an SD-OCT device (Spectralis HRA; Heidelberg Engineering, Carlsbad, CA). On the conventional SD-OCT B-scan Fig. 1. Multiple acquisition modalities on SD-OCT (Heidelberg Spectralis HRA). A. Conventional linear OCT Bscan allows good visualization of the preretinal vitreal pocket (asterisks) and retinal structures, but the outer choroidal boundary is not visible. B. Linear EDI-OCT B-scan increases visualization of the outer choroidal boundary (arrows) but decreases identification of the posterior vitreal structures. C. Combined conventional OCT and EDI-OCT B-scan yields a single comprehensive image of the posterior structures, including preretinal vitreal pocket (asterisks), retina, and choroid (arrows). EDI-OCT, enhanced depth imaging on spectral domain optical coherence tomography.