RCGP SCA Algorithm — UK Primary Care
Acute visual loss is an ophthalmological emergency until proven otherwise. Sudden painless monocular loss or a curtain/shadow defect needs immediate assessment through the local eye emergency/stroke pathway — do not delay transfer for primary-care investigations or treatment. Most eye emergencies need same-day eye emergency assessment rather than an ambulance; use 999 for neurological features, systemic illness or unsafe transfer.
Central retinal artery occlusion is an ophthalmic and stroke emergency — there is no universally established routine treatment window; interventions such as thrombolysis depend on local specialist/stroke pathways and eligibility, so arrange immediate assessment. Giant cell arteritis is an important missed ocular emergency — start treatment immediately per the local GCA pathway, before temporal artery ultrasound/biopsy; delay risks bilateral blindness.
The monocular vs binocular distinction is the most important early differentiator — covering each eye individually in consultation takes 10 seconds and separates ocular pathology from neurological pathology. New binocular diplopia in an elderly patient with hypertension strongly suggests microvascular cranial nerve palsy (III, IV, VI) — usually self-limiting but must exclude posterior communicating artery aneurysm (third nerve palsy with ptosis and dilated pupil = aneurysm until proven otherwise). Hydroxychloroquine retinopathy is detected through commissioned hospital retinal monitoring (OCT, fundus autofluorescence ± visual fields), not routine optometrist review — confirm the patient is enrolled.
Dry eye disease is a common cause of "blurry vision" in primary care and most do not need specialist review. A simple test: ask if vision improves after blinking — yes = dry eye/surface disease. AMD is a leading cause of sight loss in older adults. Suspected wet AMD requires urgent referral to a macula service, normally within 1 working day; NICE NG82 advises anti-VEGF treatment as soon as possible and within 14 days of referral where indicated.
The pinhole test is the most underused tool in primary care — it can distinguish refractive error (improves with pinhole) from pathological visual loss (does not improve). RAPD is the key sign for optic nerve disease — it indicates asymmetric afferent input and is present in optic neuritis, CRVO, and CRAO. A complete third nerve palsy with a dilated pupil (surgical third nerve) must be differentiated from a pupil-sparing microvascular third nerve palsy — dilated pupil = aneurysm, emergency CT angiography required.
GCA bloods should be sent simultaneously with starting prednisolone — never delay treatment waiting for results. ESR can be normal in GCA, so CRP is sent alongside. In retinal artery occlusion a cardiac embolic source such as AF may be found — ECG and vascular risk assessment are arranged in hospital or through the stroke pathway. In optic neuritis, specialist MRI helps assess demyelinating disease, but ischaemic, inflammatory, infective, compressive and toxic causes must also be considered.
NICE NG82: refer suspected wet AMD urgently to a macula service (normally within 1 working day) and offer anti-VEGF as soon as possible, within 14 days of referral where indicated — delay risks permanent central vision loss. Optometrist-led triage pathways (primary eyecare acute referral services, PEARS) are available in most NHS areas and can see urgent eye problems promptly, freeing A&E and ophthalmology capacity for genuine emergencies.
Next steps: see Giant cell arteritis · Stroke and TIA · Glaucoma · Macular degeneration · Dry eye disease
In GCA, untreated patients risk visual loss in the fellow eye — start glucocorticoids per the local pathway before ultrasound/biopsy. In diabetic eye disease, optimise HbA1c and BP to individual targets alongside, never instead of, eye referral. Intravitreal anti-VEGF preserves vision in wet AMD — which is why anti-VEGF treatment for late AMD (wet active) is recommended in NICE NG82 (2018).
AREDS2-formula supplements are considered only on ophthalmology advice for the relevant stage of AMD. Diabetic eye screening is a key preventive intervention in diabetes — people who do not attend screening are at higher risk of preventable sight loss.
GCA steroid tapers are prolonged, specialist-led and individualised. Tocilizumab (IL-6 inhibitor) is recommended in NICE TA518 (2018) for relapsing or refractory GCA (stopped after at most 1 year of treatment), allowing faster steroid taper and reducing cumulative steroid-related harm. AMD same-day emergency services (Macular Society) exist in most NHS regions — patients should have the service number. Pregnancy dramatically worsens diabetic retinopathy — women planning pregnancy should be offered a retinal assessment at their first preconception appointment (unless done in the last 6 months) and again during pregnancy (NICE NG3); rapid tightening of glucose control should wait until retinal assessment and any treatment.