OCT Casebook: Starting out

In the previous casebook, I suggested that a good starting point for a first or screening OCT assessment would be to undertake a line scan (horizontal and vertical), a volume scan and a scan around the disc. This week we will consider the last of these.

Most OCTs group the various ways of scanning the disc under a ‘disc’ or ‘glaucoma’ setting rather than ‘retina’ as is the case for the previously mentioned scans. It is perfectly possible to use a line scan or a volume scan to analyse a cross section of the disc, and for the assessment of glaucoma suspects or those with known risk factors, these are of value as we shall see in later casebooks. As an initial screening assessment, for baseline data gathering or general screening, we tend to use a scan designed to measure the thickness of the retinal nerve fibre layer (RNFL) at a short distance from the disc. Usually known simply as an RNFL scan, this entails the laser scanning in a ring (annular scan) around the outside of the disc.