OCT tip of the month- Full Depth Imaging(FDI), or Combined Depth Imaging(CDI).
Posterior OCT has a small window of “focus”- in other words, the depth of focus is usually from the pre retinal vitreous face to the RPE.
When we use the Enhance Depth Imaging (EDI) utility on the OCT, it moves the window of focus further posteriorly- from approximately the inner plexiform layer (IPL) to well into the choroid, and even to the sclera. This allows for much better visualization of the choriocapillaris and choroid, and allows for choroidal thickness measurement. The downside is that we lose detail of the neurosensory retinal layers- the nerve fiber layer (NFL) to the outer plexiform layer (OPL). FDI, or CDI, allows us to combine both modes of OCT to produce an image that is detailed from NFL to sclera.
Using the Heidelberg Spectralis, it’s easy to combine both techniques to get Full Depth Imaging.
- Line up a scan as usual.
- Set the ART on the screen to 100 frames
- Press the ART/Sensitivity knob on the touch screen
- Once the ART images have reached the halfway point, click on EDI
- Allow the ART frames to reach 100 in the EDI mode
The resulting image will be a combination of standard OCT and EDI OCT
Combined, or Full Depth Imaging OCT