OCT, fundus photography and angiography
- Examination
OCT gives a cross-section of the retina, photographs screen and document it, and angiography shows how blood flows and leaks. Each answers a different question.
See it in 3D: Retina · Macula · Optic disc
What it is
Ophthalmology relies on imaging that the general doctor rarely orders but often reads in reports. Optical coherence tomography (OCT) uses light to make micrometre-scale cross-sections of the retina and optic nerve. Fundus photography records the retina and is the basis of diabetic retinopathy screening and telemedicine. Fluorescein angiography, with dye injected into a vein, shows leakage, blocked capillaries and new vessels. OCT angiography shows vessels without dye.
Normal values and scales
- OCT shows macular oedema, fluid in neovascular macular degeneration, macular holes and the thickness of the nerve fibre layer in glaucoma.
- Fluorescein angiography shows capillary non-perfusion, new vessels and leakage.
- After fluorescein the skin and urine turn yellow for a day; nausea is common and severe allergic reactions are rare.
- Retinal photographs graded remotely allow diabetic screening where there are few ophthalmologists.
How it is done
- OCT: the patient looks at a target while a scan of the macula or optic disc is taken in seconds, without contact or dye.
- Fundus photography: one or more images of the posterior pole, through dilated or undilated pupils; wide-field cameras capture the periphery.
- Fluorescein angiography: dye is injected into an arm vein and serial photographs record its passage through the retinal and choroidal vessels.
- The ophthalmologist compares the images with previous ones to judge change.
How to interpret it
- Anti-VEGF treatment of macular degeneration and diabetic macular oedema is guided by repeated OCT.
- Thinning of the nerve fibre layer on OCT can precede field loss in glaucoma.
- OCT of the optic disc helps follow papilloedema and separate it from disc drusen.
Next step / Initial management
- Report of new fluid or haemorrhage at the macula: ophthalmology within days.
- Abnormal diabetic screening photograph: refer according to the grade (urgent for proliferative disease).
- Before fluorescein angiography: ask about allergy, pregnancy and kidney disease, and have resuscitation available.
- Imaging complements the clinical exam; it does not replace measuring acuity and examining the eye.
Test yourself
Think of the answer, then tap the question to see it.
Which test shows macular oedema as a cross-section without dye?
Optical coherence tomography (OCT).
What does fluorescein angiography show that OCT does not?
The dynamic passage of dye through the vessels: leakage, non-perfused capillaries and new vessels.
What expected effects follow fluorescein angiography?
Yellow discoloration of skin and urine for about a day, and sometimes nausea.
Connections
See it in 3D3
The structures of Durgical's 3D anatomy where it is found.
In Pharmacology1
Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once.
Sources: Optical Coherence Tomography (StatPearls Publishing (NCBI Bookshelf), 2024); Fluorescein Angiography (StatPearls Publishing (NCBI Bookshelf), 2023); Fundus Camera (StatPearls Publishing (NCBI Bookshelf), 2026).
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Representative model, for educational purposes only.