Vision loss is one of the highest-stakes presentations in general practice. CRAO is treated as an ocular equivalent of acute ischaemic stroke for urgent vascular assessment, but there is no universally established ophthalmic treatment window or GP-administered reperfusion treatment — ocular massage, paracentesis, hyperbaric oxygen and thrombolysis have variable evidence and are specialist-led. NICE thrombolysis windows apply to selected cerebral ischaemic stroke within organised stroke services. Giant cell arteritis is the most preventable cause of permanent blindness in adults over 50 — starting high-dose corticosteroids immediately, before biopsy results, is correct management. Any delay risks permanent, sometimes bilateral, blindness. Retinal detachment involving the macula ("macula-off") carries a much worse visual prognosis, so same-day assessment matters. Amaurosis fugax is a TIA — early stroke risk is highest in the first days, so specialist assessment within 24 h (NICE NG128).

The onset–laterality–type–pain framework localises the lesion before any examination. Sudden painless monocular loss = vascular occlusion until proven otherwise — act immediately. Central vision loss (inability to read, recognise faces) points to macular pathology. Peripheral vision loss (bumping into things, tunnel vision) points to glaucoma or retinitis pigmentosa — often asymptomatic until late. The distinction between a homonymous hemianopia (neurological, post-chiasmal) and monocular field defect (ocular, pre-chiasmal) is critical and requires careful testing of each eye separately. Always ask about metamorphopsia (straight lines appearing wavy) — this is the hallmark of macular disease and AMD conversion from dry to wet.

Anatomical localisation drives both urgency and referral destination. Anterior segment pathology (cornea, iris, lens) → urgent ophthalmology. Posterior segment (retina, choroid) → emergency ophthalmology for acute causes. Optic nerve (GCA, optic neuritis, glaucoma) → depends on cause: GCA = same day start steroids; optic neuritis = urgent neurology/ophthalmology; glaucoma = urgent outpatient. Neurological pathway (chiasm to cortex) → neurology, often with urgent MRI. Bitemporal hemianopia is pituitary adenoma until proven otherwise — urgent MRI pituitary. The RCGP SCA frequently presents visual field patterns that require anatomical localisation.

The RAPD (swinging light test) is the single most important GP examination finding for vision loss — it detects unilateral optic nerve or severe retinal dysfunction with high sensitivity and costs nothing. A positive RAPD with acute vision loss in a patient over 50 is GCA or CRAO until proven otherwise. Fundoscopy can change management in acute vision loss — a pale disc with cherry-red spot = CRAO; a swollen disc needs urgent specialist assessment. Documenting VA formally is clinically important — "vision seems reduced" is inadequate in a referral letter. Suspected true papilloedema (bilateral disc swelling with headache, vomiting, reduced consciousness, focal neurology or transient visual obscurations) requires same-day emergency neurological assessment and imaging.

ESR and CRP must not delay steroids in suspected GCA — the principle of "treat first, investigate second" applies here unambiguously. Temporal artery biopsy remains positive for up to 2 weeks after starting steroids, so treatment does not invalidate biopsy. ESR or CRP can be normal in GCA — do not use a normal ESR to exclude GCA if clinical suspicion is present. For CRAO and amaurosis fugax, the TIA pathway provides rapid carotid imaging (to detect ipsilateral carotid stenosis requiring endarterectomy), cardiac monitoring (24h ECG for AF), and antiplatelet therapy. Hydroxychloroquine: annual retinal monitoring generally begins after 5 years of use, or after 1 year if high-risk features (dose >5 mg/kg/day based on actual body weight, eGFR <60, tamoxifen or chloroquine), using OCT and fundus autofluorescence with fields and/or mfERG as indicated (RCOphth) — the prescriber ensures the monitoring referral is made.

The referral urgency in vision loss is uniquely consequence-laden — a routine referral for a same-day condition can result in permanent blindness within hours. The suspected cancer pathway applies only to suspected intraocular malignancy (uveal melanoma). Everything else with acute vision loss is same-day or emergency. Cataract extraction has one of the lowest QALY costs in all of surgery — do not delay routine referral when VA is functionally impaired. The GP's most critical role in wet AMD is timely recognition and rapid referral — delay in initiating anti-VEGF directly correlates with worse visual outcome. Suspected true papilloedema requires same-day emergency neurological assessment and imaging, not an optometrist referral.

Prednisolone for GCA must be started by the GP — this is the most time-critical prescribing decision in ophthalmic primary care. Untreated, the other eye can lose vision within days of the first. Starting steroids before biopsy is confirmed by the BSR GCA guideline (2020) as the correct approach. Anti-VEGF treatment can preserve vision in wet AMD, although response varies — the GP's role is rapid recognition and referral, not watching and waiting. Never prescribe topical corticosteroid eyedrops in primary care without ophthalmological assessment — they can worsen undiagnosed herpetic keratitis (dendrite ulcer) and can permanently damage vision.

Smoking is the most important modifiable risk factor for AMD — a fact many patients are unaware of. Framing AMD risk as a smoking-related disease resonates more powerfully than generic health messages. AREDS2-type supplementation may benefit selected people with intermediate or advanced AMD as advised by ophthalmology; it is not for all AMD. The NHS Diabetic Eye Screening Programme is one of the most successful public health initiatives in the UK — it identifies and treats sight-threatening diabetic retinopathy before symptoms develop. GP practices should have recall systems ensuring all diabetic patients attend their screening (annual, or every 2 years if low risk). Non-attendance is a significant clinical governance concern.

GCA steroid monitoring is a complex long-term primary care responsibility — relapses are common during taper and require prompt steroid dose increase. Bone protection should be addressed according to fracture risk and steroid duration, following the local GCA pathway. Self-monitoring advice (with an Amsler grid where useful) helps identify wet AMD early: "contact your eye-care professional promptly if straight lines look wavy or your central vision changes".