Author: Claude (AI), from PubMed abstracts · Reviewed by: Dr Mina Abdelmseih · Reviewed: 2026-11-15 · Review due: 2027-11-15

Educational content only. Not personalised medical advice. Clinical decisions remain the responsibility of the treating clinician.

OCT interpretation: macula and retinal nerve fibre layer

Optical coherence tomography (OCT) gives cross-sectional images of the macula, retinal nerve fibre layer (RNFL), ganglion cell layer and optic nerve head [S8]. It is central to diagnosing and monitoring macular disease [S10] [S11] and glaucoma [S4] [S7], but reliable reading needs standard terminology [S1], high-quality scans that are actually looked at [S2], and awareness of normative database limits [S3] [S5].

Key points - Read the scan, not just the colour map: visual analysis of a high-quality circle scan helps avoid both false positive and false negative glaucoma calls [S2]. - Average RNFL thickness was the most accurate single Stratus OCT parameter for glaucoma, but accuracy was lower in Asian populations [S3]. - Macular OCT is reproducible and supports detection of early glaucoma [S7]; confirm any apparent progression on at least one repeat scan after two or more baseline scans [S4]. - No commercial OCT device includes a paediatric normative database, which can lead to important interpretation errors in children [S5]. - Macular neovascularisation, diabetic macular oedema and disc swelling are best assessed with multimodal imaging, of which OCT is one part [S8] [S10] [S11].

Evidence last checked: 2026-10-17 (PubMed abstracts).

Red flags: findings that need urgent action

• New subretinal or intraretinal fluid with a grey-green macular lesion or symptoms of distortion. Suggests macular neovascularisation [S11]; needs prompt retina assessment [G1].
• Retinal thickening involving the fovea in diabetes. Diabetic macular oedema can cause vision impairment and blindness [S10].
• Peripapillary wrinkles or outer retinal creases on en face OCT. Common, distinctive signs of optic disc oedema that rule out pseudopapilledema [S8]; same-day systemic or neurological assessment [EIC expert opinion].
• Superonasal RNFL thinning with a field defect. More typical of anterior ischaemic optic neuropathy than glaucoma [S9].

Recognise it: reading the macular scan

• Layers. Use the IN•OCT consensus terms for normal bands, including the ellipsoid and interdigitation zones [S1].
• Macular neovascularisation (MNV). The CONAN term covers intraretinal, subretinal and sub-RPE neovascularisation; MNV often shows intraretinal thickening and/or subretinal exudation [S11].
• Diabetic macular oedema. Retinal thickening near or involving the fovea from fluid accumulation [S10].
• Lamellar macular hole (LMH) and mimics [S6]:

Confirm it: reading the RNFL and optic nerve scan

1. Check quality and artefacts. Inspect the circle scan itself [S2]; recognise common artefacts and optimise acquisition [S8].
2. Match structure and function. Compare the location of abnormal field points with regions of abnormal ganglion cell and RNFL thickness [S2].
3. Sector pattern. In a systematic review of 39 studies, glaucoma thinned mainly superotemporal, inferotemporal and inferonasal RNFL, while AION mostly thinned superonasal RNFL; glaucoma also showed larger cups and thinner Bruch's membrane opening-minimum rim width [S9].
4. Disc swelling. RNFL and GC-IPL thickness have limits when swelling is severe; SD-OCT is the most sensitive way to identify buried disc drusen [S8].
5. Children. Use published paediatric normative data, not the device's adult database [S5].

Manage it: using OCT at each resource tier

Before acting on this section, check the national and local guidelines, product information and regulatory approvals that apply where you practise. See the medical disclaimer.

Tier A (primary care / no specialist)

OCT interpretation is a Tier B / Tier C skill. Where an OCT report reaches primary care, act on it using the Refer when table below.

Tier B (general eye clinic)

1. Combine OCT with fundus examination and other imaging for DME and MNV [S10] [S11].
2. Do not label glaucoma on the colour map alone; review scan quality and correlate with the field [S2].
3. Take extra care with normative comparisons in Asian patients [S3] and children [S5].

Tier C (specialist centre)

1. Glaucoma progression. A RNFL loss slope greater than -1 per year is associated with a higher risk of future field loss, and ganglion cell complex change is often earlier than RNFL change [S4]. Use two or more baseline scans and confirm change on a repeat scan [S4].
2. Neuro-ophthalmology. Use transverse axial, en face and circular tomograms qualitatively, and adduction scans in papilledema, to expose folds [S8].
3. Macular disease. Use OCT within multimodal imaging (OCT angiography, dye angiography, autofluorescence, wide-field photography) to diagnose and guide treatment [S10] [S11].
4. Use standard nomenclature in reports and research [S1] [S6].

Refer when

Pitfalls

• Trusting colour-coded probability maps without inspecting the scan [S2].
• Using adult normative data in children [S5].
• Calling progression from one follow-up scan [S4].
• Confusing pseudohole or ERM foveoschisis with lamellar hole [S6].
• Assuming RNFL thinning means glaucoma when the pattern fits AION [S9].
• Relying on RNFL thickness when disc swelling is severe [S8].

Evidence notes

• The meta-analysis used an older time-domain device (Stratus) [S3]; accuracy of modern devices is not covered by these sources.
• The paediatric normative review focuses on Spanish and European populations [S5].
• Most sources are narrative reviews or consensus statements; one systematic review [S9] and one meta-analysis [S3] are included.
• The search returned many off-topic records (coronary and skin OCT, psychiatric and neurological biomarkers).
• Not covered by these sources: specific thickness cut-offs for DME, scan protocols by device, segmentation error rates, and accuracy data for modern spectral-domain glaucoma parameters.

Related articles

• OCT angiography
• Artificial Intelligence in Retina and OCT
• Diabetic Macular Oedema

References

See the numbered source list below. Each marker [S#] links to its PubMed and DOI record.