Retinal nerve fiber layers (RNFL) are proving to be useful biomarkers in various aspects of disease diagnosis and monitoring and, with today’s technology, clinicians have a number of ways to image them. Among the options are spectral domain (SD) OCT and swept source (SS) OCT. Now, researchers are showing that SD-OCT and SS-OCT have good-to-excellent agreement between them. This means OCT angiography using SS-OCT (SS-OCTA) is sufficiently capable of providing RNFL thickness, according to the Singapore-based team.

The investigators measured RNFL thicknesses using both SD-OCT and SS-OCTA in 57 participants—12 with glaucoma, eight with ocular hypertension and 74 normal eyes. The participants were all scanned with the two OCT instruments on the same day and with the same experienced operator. Circumpapillary RNFL thicknesses were automatically segmented for SD-OCT and manually segmented for SS-OCTA scans.

They reported excellent agreement globally and in the inferior and superior quadrants, and good agreement in the temporal and nasal quadrants. The team noted eyes of ocular hypertensive patients showed lower agreeability in the nasal quadrant. SS-OCTA RNFL thickness was on average 3µm thicker than SD-OCT, particularly in the nasal and temporal quadrants.

Tan B, Chua J, Harish T, et al. Comparison of a commercial spectral-domain OCT and swept-source OCT based on an angiography scan for measuring circumpapillary retinal nerve fibre layer thickness. Br J Ophthalmol. October 4, 2019. [Epub ahead of print].