[Full depth imaging: a new imaging technique using optical coherence tomography (OCT)]

The aim of this study was to evaluate the full depth imaging (FDI) mode as a new acquisition technique with spectral domain (SD) optical coherence tomography (OCT) from Heidelberg Engineering for illustrating vitreoretinal and choroidal structures with high contrast.

Patients with different diseases such as age-related macular degeneration, chorioretinopathia centralis serosa, diabetic retinopathy and epiretinal gliosis were examined with the FDI mode. For comparison, we also examined healthy probands with conventional OCT and the enhanced depth imaging (EDI) mode. FDI images were obtained with a manual acquisition technique. First, 100 conventional OCT scans of the vitreoretinal interface were averaged. After manual switching to the EDI mode the previous averaged image was overlayed with EDI images until vitreous, retina and choroid were projected in one comparably sharp image.

The FDI mode enables SD-OCT images showing the vitreoretinal interface and deep choroid structures with a high contrast. The new acquisition mode has a few limitations: it is only possible to perform a single linear scan, a raster scan is not possible. The FDI mode is a manual acquisition technique and not automated yet.

By a combination of averaged images of the vitreoretinal interface with the help of conventional SD-OCT scans with EDI OCT scans the FDI mode exhibits a simultaneous contrast image of the posterior vitreous, the retina and the choroid. Whereas the application of OCT was focused to evaluate the retina-retinal pigment epithel complex, the routine reinforcement of FDI scans could additionally show potential vitreous and choroidal pathologies. As the FDI mode is not an automated application yet it may be too complex to use for routine diagnostics at the moment.