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OphthoSpace

Interpret / OCT Lab

The retina in cross section

Optical coherence tomography slices the macula at the resolution of histology. Learn the layers, then read real scans the same way every time: the foveal contour, the fluid and which compartment it is in, what the pigment epithelium is doing, and only then the impression.

Read the scan

OCT B-scan through the macula, diagnosis hidden

Kermany DS, Zhang K, Goldbaum M. Labeled Optical Coherence Tomography (OCT) and Chest X-Ray Images for Classification. Mendeley Data, V2 (2018). CC BY 4.0. Cut from the dataset's contact sheets; research and educational use, not clinical diagnosis. Dataset. Greyscale unaltered; brightness and contrast are the viewer's own controls.

Read it in order

1. Foveal contour

2. Fluid

3. The RPE

4. Impression

The layers, vitreous to choroid

Alternating bright and dark bands: plexiform layers and the nerve fibre layer are bright, the nuclear layers dark, the RPE the brightest line of all.

  1. 01

    Internal limiting membrane ILM

    The bright inner surface of the retina against the black vitreous. Epiretinal membranes lie on it.

  2. 02

    Retinal nerve fibre layer RNFL

    Bright, thickest near the disc, absent at the fovea. Measured around the disc for glaucoma.

  3. 03

    Ganglion cell layer GCL

    Darker, thick around the fovea and thin at it; lost early in glaucoma and optic neuropathy.

  4. 04

    Inner plexiform layer IPL

    Bright: synapses between bipolar and ganglion cells.

  5. 05

    Inner nuclear layer INL

    Dark: the bipolar, horizontal and amacrine cell bodies. Cystoid spaces of macular oedema sit here and in the outer plexiform layer.

  6. 06

    Outer plexiform layer OPL

    Bright: photoreceptor synapses. Hard exudate collects here as bright dots with shadows.

  7. 07

    Outer nuclear layer ONL

    Dark and thick at the fovea: the photoreceptor cell bodies, all cones at the centre.

  8. 08

    External limiting membrane ELM

    A thin bright line; its integrity predicts visual recovery.

  9. 09

    Ellipsoid zone EZ

    A bright band of photoreceptor inner segments; disruption here correlates with reduced vision.

  10. 10

    Retinal pigment epithelium RPE

    The brightest outer band, with Bruch's membrane beneath. Drusen bump it; a pigment epithelial detachment lifts it; atrophy loses it and lets light through to the choroid.

  11. 11

    Choroid Choroid

    Vessels as dark ovals below the RPE, on newer scans down to the sclera.

Normal beside abnormal

oct macula image, diagnosis hidden
AAtlas
oct macula image, diagnosis hidden
BAtlas

What separates them?

Look first. Say out loud which is which and why, then reveal.

Every pair is two real photographs from the atlas; nothing is drawn on them.

More OCT in the atlas

Taught here, not yet illustrated

These patterns matter and are described; a verified, openly licensed scan of each has not yet been found, so no image is shown rather than an invented one.

Macular hole
A full-thickness defect at the fovea with cystic edges; the contour is a hole rather than a pit. Vision loss is central and distortion is the complaint.
Epiretinal membrane
A bright line on the inner surface wrinkling the retina beneath, with a distorted or lost foveal pit. Metamorphopsia is the symptom.
Central serous chorioretinopathy
A smooth dome of subretinal fluid with a flat or slightly bumped RPE and a thick choroid, in a younger patient, often a stressed one.
Retinal detachment on OCT
The neurosensory retina lifted away from the RPE by a dark space, at the edge of the scan or across it.

Correlate every OCT with the fundus photograph: they answer different questions. Read the fundus