Optic disc !
The optic disc is the pale round spot at the back of the eye where the optic nerve leaves; it has no light receptors, so it forms the blind spot.
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What it is
The pale round spot where the optic nerve leaves the eye.
What it does
Has no light receptors (the blind spot); doctors look at it for glaucoma and brain swelling.
Key facts
- Where
- Nasal to the macula; ~1.5–1.8 mm
- Blood supply
- Central retinal artery emerges here; short posterior ciliary arteries
- Function
- Exit of the optic nerve; blind spot; cup-to-disc ratio checked in glaucoma
Relations
- Contents
- Axons of the retinal ganglion cells converging to form the optic nerve, with the central retinal artery and vein entering and leaving near its centre
- Behind
- Lamina cribrosa, a sieve of sclera where the axons pass out and gain myelin, and then the optic nerve
- Lateral
- Macula, on the temporal side, linked to it by the papillomacular bundle
- Medial
- Nasal retina, whose nerve fibres run straight to the disc
How to find it
Found on fundoscopy by following any retinal vessel back to where the branches converge; with the patient looking ahead, the ophthalmoscope is aimed slightly nasally. A normal disc has a pink-orange rim, sharp margins and a pale central cup.
Examination
- Fundoscopy for colour, margins, cup and rim; spontaneous venous pulsations at the disc argue against raised pressure, though some healthy people lack them
- Swinging flashlight test: a relative afferent pupillary defect points to optic nerve disease on that side
- Visual fields: an enlarged blind spot in papilloedema, arcuate defects in glaucoma
On imaging
OCT measures the retinal nerve fibre layer and the rim; B-scan ultrasound or autofluorescence shows buried disc drusen; with a swollen disc, brain imaging comes before lumbar puncture to measure the opening pressure.
Common problems
- Glaucoma: the cup in the centre of the disc widens as nerve fibres are lost.
- Papilloedema: the disc swells when pressure inside the skull is high (a warning sign).
How it is diagnosed
Looking at the disc with an ophthalmoscope, eye-pressure measurement, OCT of the nerve fibres and visual field tests.
Treatment
- Treat the cause: lower eye pressure in glaucoma; find and treat raised pressure in the skull.
Clinical notes
- Disc pallor (optic atrophy) follows long-standing damage of any cause: compression, ischaemia, glaucoma, inflammation
- Anterior ischaemic optic neuropathy: sudden painless loss with a pale swollen disc; giant cell arteritis is the cause to rule out in older patients
- Idiopathic intracranial hypertension, typically in young women with obesity, presents with papilloedema, headache and brief visual blackouts
- Foster Kennedy syndrome: one atrophic and one swollen disc, classically from a frontal tumour
Anatomical variants
- Optic disc drusen: buried calcified deposits that mimic papilloedema (pseudopapilloedema)
- Tilted, oval disc in myopia, with a crescent of exposed sclera or choroid at its edge
- Myelinated nerve fibres: white feathery patches at the disc margin, harmless
- Large physiological cup, usually the same in both eyes and often familial
Development
Ganglion cell axons grow back through the optic stalk; the hyaloid artery that ran through it regresses, leaving the central retinal artery, and a glial tuft on the disc (Bergmeister papilla) is a common remnant.
Memory aid
ISNT rule: the healthy rim is usually thickest Inferiorly, then Superiorly, Nasally and Temporally; breaking this order suggests glaucoma.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
What is papilloedema and what are its signs at the optic disc?
Disc swelling from raised intracranial pressure, usually bilateral: blurred margins, raised disc, hidden vessels, haemorrhages; early vision is spared.
How does the optic disc change in glaucoma?
The cup widens as the neuroretinal rim thins, especially at the upper and lower poles; asymmetry between the eyes is a warning sign.
Why is the blind spot temporal to fixation in the visual field?
The optic disc, which has no photoreceptors, lies nasal to the fovea.
What does the ISNT rule describe at the optic disc?
The healthy rim is usually thickest Inferiorly, then Superiorly, Nasally and Temporally; breaking this order suggests glaucoma.
In an older patient with sudden painless loss of vision and a pale swollen disc, which cause must be ruled out?
Giant cell arteritis, as a cause of anterior ischaemic optic neuropathy.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- discus nervi optici TA2 6788
- Official Spanish (DeCS)
- Disco Óptico DeCS D009898
- English (TA2)
- Optic disc
- Also called
- optic nerve head · blind spot · papilla nervi optici
Related
Sources: Terminologia Anatomica (TA2); DeCS; Papilledema; Anatomy, Head and Neck: Retina.
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Representative model, for educational purposes only.
