Ischaemic optic neuropathy

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Ischaemic optic neuropathy results from inadequate perfusion of the optic nerve. In anterior disease, the optic disc becomes swollen during the acute phase and later develops pallor as the injury evolves. Visual loss may affect an upper or lower portion of the field and can be substantial despite a relatively comfortable eye. Posterior ischaemic injury is less common and may initially lack disc swelling, usually requiring specialist assessment of the clinical context and alternative causes. The key immediate distinction is whether arteritis is driving the ischaemia.

Non-arteritic anterior ischaemic optic neuropathy, commonly abbreviated NAION, is associated with a susceptible optic-disc structure and vascular or systemic factors. A crowded disc with a small cup can increase vulnerability, while diabetes, hypertension, smoking and obstructive sleep apnoea are relevant to assessment. These associations do not prove that a particular action caused the event. Blood-pressure fluctuations and medication effects require thoughtful review; telling a patient to abandon antihypertensive treatment independently can create a different vascular hazard.

Arteritic anterior ischaemic optic neuropathy demands a different response because untreated giant-cell arteritis can threaten the fellow eye. Ask about new headache, scalp pain, jaw fatigue or pain while chewing, tongue symptoms, shoulder or hip stiffness, weight loss and constitutional illness. Some patients present mainly with visual symptoms. Investigation and treatment must proceed in parallel when suspicion is strong. After a non-arteritic diagnosis has been established, explain the limits of available acute treatment while arranging practical visual support and attention to modifiable health risks.

Key points

Anterior ischaemic optic neuropathy affects the optic nerve head and commonly produces acute disc swelling with a monocular field deficit.
Non-arteritic disease often presents as sudden painless loss, sometimes noticed on waking, with an altitudinal or other field defect.
Arteritic disease, usually related to giant-cell arteritis in this setting, needs immediate treatment to protect remaining vision.
A normal inflammatory marker or absence of headache cannot independently exclude giant-cell arteritis when the ocular and clinical findings are concerning.
No treatment has reliably restored vision in established NAION; management includes assessment of vascular, sleep-apnoea and medicine-related factors.
Do not independently stop essential cardiovascular treatment or prescribe aspirin as a guaranteed method of preventing fellow-eye involvement.
The MHRA's semaglutide warning applies to Wegovy, Ozempic and Rybelsus; confirmed NAION is the point for discontinuing that medicine.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Non-arteritic perfusion disturbance

A susceptible optic-disc structure interacts with vascular and systemic factors to produce ischaemic injury. The precise mechanism in an individual episode is often uncertain.

Arteritic vascular inflammation

Giant-cell arteritis can compromise the vessels supplying the optic nerve and cause severe visual loss. The accompanying systemic symptoms may be prominent or relatively limited.

Systemic and medicine context

Sleep apnoea, diabetes, hypertension, anaemia and selected medicines can be relevant to the assessment. An association requires clinical interpretation rather than an assumption of individual causation.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Optic nerve head ischaemia
Reduced perfusion injures axons at the optic disc and produces acute swelling. The resulting functional loss may affect central acuity, colour perception or a portion of the field.
2
Crowded disc vulnerability
A small physiological cup can leave limited space within the nerve head. Swelling and local perfusion disturbance may interact within this anatomically susceptible structure.
3
Evolution towards atrophy
As acute swelling resolves, damaged axons can leave optic-disc pallor and persistent field defects. Apparent structural settling does not necessarily mean that lost function has recovered.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Sudden painless field loss

A persistent dark or missing area, often affecting the upper or lower field of one eye, with acute disc swelling supports anterior optic-nerve ischaemia.

Arteritic warning pattern

Severe visual loss, a pale swollen disc or preceding transient visual symptoms in an older adult should trigger a focused search for giant-cell arteritis.

Vascular and sleep context

Diabetes, hypertension, smoking, anaemia, renal disease or symptoms of sleep apnoea help identify relevant medical issues, without independently confirming the ocular diagnosis.

Medicine exposure

Ask about prescribed and privately obtained semaglutide, erectile-dysfunction drugs and amiodarone, then coordinate any medicine change with the relevant prescriber and eye specialist.

Red flags requiring action

New visual loss with jaw or tongue claudication, scalp tenderness, constitutional symptoms or polymyalgic symptoms requires immediate consideration of giant-cell arteritis.
A profoundly reduced acuity or strikingly pale swollen disc increases concern for arteritic disease, but appearance alone cannot safely settle the diagnosis.
Sudden or rapidly worsening vision during semaglutide treatment requires urgent eye assessment; confirmed NAION requires semaglutide discontinuation under current MHRA advice.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Urgent acuity, pupil, disc and field assessmentFirst step
Why
Localise visual dysfunction and assess the extent of injury.
Interpretation and limitations
An afferent pupil defect and swollen disc support optic neuropathy, but retinal vascular occlusion, inflammation and other alternatives require a complete ocular examination.
02
ESR, CRP and full blood count when arteritis is possible
Why
Support prompt assessment of inflammation, anaemia and platelet changes.
Interpretation and limitations
Inflammatory results contribute to probability but cannot safely rule out giant-cell arteritis alone; treatment must not await results when vision is threatened.
03
Temporal-artery and vascular investigation through the GCA pathway
Why
Obtain diagnostic evidence when an arteritic cause is suspected.
Interpretation and limitations
Specialist ultrasound or biopsy helps establish the diagnosis, but arranging confirmation must not postpone glucocorticoids for a clinically convincing visual emergency.
04
Blood pressure, metabolic and sleep-apnoea assessment
Why
Identify relevant vascular risk and potentially treatable systemic disease.
Interpretation and limitations
Review glycaemic control, lipids and sleep symptoms in context; correcting risk factors supports general health even though a particular intervention is not proven to reverse NAION.
05
OCT, formal fields and selected neuroimaging
Why
Document structural and functional change or investigate an atypical course.
Interpretation and limitations
Persistent progression, unusual findings or diagnostic uncertainty may justify brain and orbital imaging; serial OCT alone does not distinguish every cause of optic-disc swelling.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Optic neuritis

Subacute loss with movement-related pain and colour impairment often suggests inflammation, particularly in younger adults. Atypical inflammatory disease can overlap with the appearance of ischaemic injury.

Retinal vascular occlusion

Acute painless loss can arise from retinal rather than optic-nerve vascular disease. Dilated examination and selected retinal imaging help identify the affected structure and required urgent pathway.

Compressive or infiltrative neuropathy

Progressive, atypical or persistently worsening optic dysfunction can indicate a structural lesion. Specialist-directed orbital and brain imaging may be needed when the clinical course does not fit.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Possible arteritisTreat a threatened eye while confirming the causeFirst stepAcute ischaemic-looking visual loss is accompanied by clinical concern for giant-cell arteritis.

1Contact ophthalmology and the urgent GCA service on the same day, communicating the visual findings and systemic history.
2Take blood samples promptly if this does not delay treatment, and start the specialist-agreed high-dose glucocorticoid pathway.
3Arrange vascular confirmation and ongoing rheumatology care, explaining that treatment aims particularly to prevent additional irreversible visual injury.

02Confirmed non-arteritic diseaseReview health risks and support visual functionSpecialist assessment has established NAION and adequately addressed the arteritic differential.

1Explain the expected evolution and the absence of a proven treatment that reliably restores the damaged optic nerve.
2Review blood pressure, diabetes, smoking, anaemia and possible sleep apnoea with primary care and relevant specialists.
3Arrange follow-up of fields and function, discuss driving and work implications, and offer low-vision or rehabilitation support when needed.

03Medicine safetyApply the specific semaglutide warningA patient using semaglutide develops sudden visual loss or receives a confirmed NAION diagnosis.

1Ask about private prescriptions as well as medicines recorded in the NHS record, and arrange urgent ophthalmic assessment for sudden or rapidly worsening loss.
2AlternativeIf NAION is confirmed, discontinue semaglutide and coordinate an alternative diabetes or weight-management plan with the prescriber.
3Report a suspected adverse reaction through the Yellow Card scheme and avoid extending the specific warning automatically to every other GLP-1 medicine.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

Treats the arteritic process when giant-cell arteritis threatens vision, rather than serving as routine therapy for NAION.

Glucocorticoids for suspected arteritic visual loss

BSR guidance conditionally supports intravenous methylprednisolone 500 mg to 1 g daily for up to three consecutive days in acute or intermittent visual loss, followed by oral treatment. If intravenous treatment is not immediately possible, oral prednisolone 60–100 mg daily for up to three days is a bridge and must not be delayed while intravenous access is arranged.

Arrange same-day specialist care and an explicit subsequent oral regimen and monitoring plan. Assess glucose, blood pressure, infection and relevant comorbidity, but do not postpone urgent treatment for confirmatory testing.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Permanent field and acuity loss

Optic-nerve ischaemia can leave enduring visual impairment that affects reading, navigation and work. Support should be based on actual function rather than disc appearance alone.

Fellow-eye involvement

A later event can affect the other eye, particularly when an arteritic process remains untreated. New symptoms require urgent reassessment rather than assuming an identical benign course.

Treatment and risk-management harms

Unnecessary steroids, inappropriate antithrombotic prescribing or independent withdrawal of essential medicines can add harm. A clear diagnosis and coordinated prescribing decisions reduce avoidable treatment risk.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Review acuity, visual fields and optic-disc evolution; continuing deterioration beyond the expected early period should prompt reconsideration of the diagnosis.
For arteritic disease, maintain coordinated ophthalmology and rheumatology monitoring of symptoms, inflammation, treatment toxicity and any new visual event.
For NAION, follow the agreed vascular and sleep assessment and ensure the patient understands which medicine changes were actually recommended.
Explain that another episode in the fellow eye is possible and that new visual loss needs urgent reassessment rather than waiting for a routine appointment.
Check the practical consequences for reading, mobility, employment and driving, and arrange support for persistent field or acuity impairment.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Aspirin is not a proven ocular rescue

Aspirin may be appropriate for an established cardiovascular indication, but it has not reliably been shown to restore NAION vision or prevent fellow-eye disease. Avoid promising an ocular benefit.

Blood-pressure review is individual

Both vascular disease and excessive hypotension can be relevant to optic-nerve perfusion. The appropriate response is a coordinated review, not automatic withdrawal or retiming of every antihypertensive.

Interpret the semaglutide frequency carefully

The February 2026 MHRA warning describes NAION as a very rare associated adverse effect, affecting up to one in ten thousand users. This category should not be confused with a study-specific annual incidence estimate.

A pale disc needs context

Severe pallid swelling raises concern for arteritis, but diagnosis integrates symptoms, age, inflammation and specialist examination. An appearance suggestive of non-arteritic disease is not a substitute for considering GCA.

11Common pitfallsFrequent interpretation and management errors.

01
Labelling an older patient's acute swollen-disc visual loss NAION before assessing for arteritic disease.
02
Waiting for temporal-artery biopsy or a repeat inflammatory marker before treating clinically suspected GCA with threatened vision.
03
Promising that steroids, aspirin or a procedure will restore NAION vision despite the lack of established benefit.
04
Stopping cardiovascular medicines without prescriber discussion or overlooking privately prescribed semaglutide when taking the drug history.