Concepts

OCT: cross-sections of the retina

Optical coherence tomography (OCT) builds cross-sectional images from echoes of near-infrared light, much as ultrasound does with sound, but at micrometre scale.[16] One slice is a B-scan; a volume is a stack of B-scans.

Through the optic disc, OCT shows the depth and shape of the cup and the thickness of the retinal nerve fibre layer (RNFL), which is thinner in glaucoma.[17]

cup depthrimlamina cribrosavitreoustop view · scan linesnerve fibre layer (RNFL)other retinal layersRPEchoroidsclera
RNFL at the disc edge
90%
of the healthy thickness
Cup depth
1.3×
the healthy depth
Interactive SchematicSchematic B-scan through the optic nerve head. Raise the damage to thin the RNFL and deepen the cup; the inset shows where the slice is taken.
Key facts
  • OCT is non-contact and takes seconds, which is why it is routine in glaucoma clinics.
  • RNFL thickness is usually measured on a circle around the disc and compared with age-matched normal values.
In GlaucomAI

The LSMU OCT scans arrived as screen recordings. The patient cards show each recording's deepest-cup frame; the phenotype doesn't use OCT measurements yet.

References on this page

  1. 16.Huang D, Swanson EA, Lin CP, et al. Optical coherence tomography. Science. 1991;254(5035):1178–1181. PubMed search ↗
  2. 17.Schuman JS, Hee MR, Puliafito CA, et al. Quantification of nerve fiber layer thickness in normal and glaucomatous eyes using optical coherence tomography. Arch Ophthalmol. 1995;113(5):586–596. PubMed search ↗
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