Combined depth imaging technique on spectral-domain optical coherence tomography

Purpose: To describe a technique to obtain combined images of vitreoretinal and choroidal structures using spectral-domain (SD) optical coherence tomography (OCT) and to evaluate applicability in normal eyes and limitations in eyes with cataract.

Design: Prospective, observational case series.

Methods: Three different foveal scans, including conventional SD OCT, enhanced depth imaging OCT and the novel method called combined depth imaging (CDI) OCT, were obtained in 42 eyes of healthy volunteers and in 26 eyes with cataract using the Heidelberg Spectralis HRA (Heidelberg Engineering). The CDI OCT images were obtained manually using an image modification process that enhances the vitreoretinal interface first and then the choroid, while averaging 100 separate OCT scans. The visualization of the inner border of the preretinal pocket and the outer border of the choroid was graded by independent masked observers for each OCT scan method.

Results: The CDI technique was able to create a good-quality combined image of the posterior structures in all the eyes, including eyes with cataract. The agreement between the grading performed by the independent observers was high for both the inner border of the vitreal pocket (κ, 0.86; P < .001) and the outer choroidal border (κ, 0.90; P < .001). CDI OCT was equivalent to conventional SD OCT in visualizing the vitreal pocket (P = .445 for normal eyes, P = .162 for eyes with cataract) and was equivalent to enhanced depth imaging OCT in visualizing the outer choroidal border (P = .660 for normal eyes, P = .329 for eyes with cataract). CDI OCT was superior to conventional SD OCT and enhanced depth imaging OCT in visualizing both of the structures (P < .001).

Conclusions: The manual technique of CDI OCT is highly sensitive to visualize posterior vitreoretinal and choroidal structures into a single full-depth image and is not affected by mild to moderate cataract.