OCT Biomarkers in Diabetic Macular Oedema
Last updated: October 2026
Short answer: OCT biomarkers in diabetic macular oedema are features that help predict vision and treatment response. The most useful are central subfield thickness, intraretinal and subretinal fluid, hyperreflective foci, disorganisation of the retinal inner layers (DRIL), ellipsoid zone and external limiting membrane integrity, and vitreomacular traction. Integrity of the outer retina and absence of DRIL predict better vision.
Key biomarkers at a glance
| Biomarker | What it looks like | Why it matters |
|---|---|---|
| Central subfield thickness (CST) | Mean thickness in the central 1 mm | Defines centre-involving DME and tracks response; correlates only moderately with vision |
| Intraretinal fluid (IRF) | Hyporeflective cysts within the retina | Main sign of active DME; very large cysts may suggest chronic damage |
| Subretinal fluid (SRF) | Fluid between the retina and RPE | A distinct DME pattern; its prognostic meaning varies between studies |
| Hyperreflective foci (HRF) | Small bright dots in the retinal layers | Thought to reflect inflammation or lipid; many clinicians consider steroids when they are numerous |
| DRIL | Inner retinal layers cannot be told apart in the central 1 mm | Associated with worse vision, even after the oedema resolves |
| EZ / ELM disruption | Breaks in the outer retinal bands | Predicts poorer final vision |
| Vitreomacular traction / ERM | Vitreous or membrane pulling on the retinal surface | May reduce the response to injections; consider vitrectomy |
Using biomarkers in practice
- Before treatment: record CST, fluid type, HRF, DRIL, EZ/ELM status and the vitreoretinal interface.
- Anti-VEGF is usually first line for centre-involving DME with reduced vision. See diabetic retinopathy guide.
- Consider steroids (for example, a dexamethasone implant) if response is poor after several anti-VEGF injections, in pseudophakic eyes, or when there are many hyperreflective foci and frequent visits are difficult.
- Consider surgery when traction or a thick ERM is clearly holding the oedema.
- Set realistic expectations: DRIL and outer retinal damage can limit vision even if the macula becomes dry.
Frequently asked questions
What is DRIL on OCT?
Disorganisation of the retinal inner layers: the ganglion cell, inner plexiform, inner nuclear and outer plexiform layers cannot be distinguished in the central macula. It is associated with worse visual acuity in DME.
What do hyperreflective foci mean in DME?
They are small bright dots thought to represent inflammatory cells or lipid deposits. Many clinicians consider steroid treatment when they are numerous.
Which OCT findings predict poor vision in DME?
DRIL and disruption of the ellipsoid zone and external limiting membrane are the strongest predictors of poorer final vision.
Related: OCT reading tips and DRCR protocols.
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