The optic disc: cup, rim and colour
- Anatomy and physiology
The optic disc is where a million nerve fibres leave the eye. Its cup, rim, colour and edges show glaucoma, optic atrophy and raised intracranial pressure.
See it in 3D: Optic disc · Optic nerve · Central retinal artery
What it is
The optic disc (optic nerve head) is where the axons of about a million retinal ganglion cells gather and leave the eye through the lamina cribrosa to form the optic nerve. It has no photoreceptors, which creates the blind spot. On fundoscopy it is a pink-orange oval with a central pale depression, the cup. The neuroretinal rim between the cup and the edge is made of the nerve fibres themselves.
Clinical anatomy
- Neuroretinal rim: the nerve fibres; normally thickest at the inferior pole, then superior, nasal and temporal.
- Cup: the central depression without nerve fibres; the cup-to-disc ratio is usually under about 0.5.
- Central retinal artery and vein enter and leave through the centre of the disc.
- Lamina cribrosa: a sieve of connective tissue through which the axons pass, visible at the base of a deep cup.
Physiology
- The nerve fibre layer carries the visual signal of the whole retina to the brain.
- Spontaneous venous pulsation at the disc is often visible and is lost when intracranial pressure rises.
- The disc has no photoreceptors, giving the physiological blind spot about 15 degrees temporal to fixation.
Clinical correlation
- Glaucoma enlarges the cup, especially vertically, and thins the rim, often first at the poles; a cup asymmetry between the eyes is suspicious.
- A small haemorrhage on the disc edge is a sign of glaucoma activity.
- Pallor means optic atrophy (after optic neuritis, compression, ischaemia, toxins).
- Blurred margins with elevation and haemorrhages mean disc swelling (papilloedema, optic neuritis, ischaemia).
Next step / Initial management
- Cup-to-disc ratio of about 0.6 or more, a cup asymmetry between the eyes, a notch or a disc haemorrhage: ophthalmology for glaucoma assessment.
- Bilateral disc swelling: urgent brain imaging (papilloedema pathway).
- Unexplained pallor: MRI of the brain and orbits and ophthalmology.
- Record the disc appearance in the notes or with a photograph for comparison.
Test yourself
Think of the answer, then tap the question to see it.
What is the neuroretinal rim made of?
The axons of the retinal ganglion cells leaving the eye.
Which disc findings suggest glaucoma?
An enlarged or vertically elongated cup, rim thinning or notching, cup asymmetry between the eyes and disc haemorrhages.
What does optic disc pallor mean?
Optic atrophy: loss of nerve fibres from a previous neuropathy.
Elsewhere in DurgiPedia
Connections
See it in 3D3
The structures of Durgical's 3D anatomy where it is found.
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: Open Angle Glaucoma (StatPearls Publishing (NCBI Bookshelf), 2024); Papilledema (StatPearls Publishing (NCBI Bookshelf), 2025); Neuroanatomy, Retina (StatPearls Publishing (NCBI Bookshelf), 2026).
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Representative model, for educational purposes only.