Central retinal artery – majority of inner retina blood circulation.
Cilioretinal artery – 15-30% of the circulation. (cilioretinal artery occlusion happens about 5% cases – watch out for GCA).
Branch retinal artery occlusion (BRAO)
- 40% of cases.
- Retinal emboli is the cause.
- Painless loss of vision – 3/4 has 6/12 vision or better.
- Sectoral retinal opacification with retinal oedema.
- Monitor for iris neovacularisation (rare).
Central retinal artery occlusion (CRAO)
- Elderly male.
- Bilateral cases 1-2%.
- Sudden painless loss of vision +/- amaurosis fugax.
- RAPD present
- Rubeosis usually within 4-5 weeks (20% cases).
- Cherry red spot at fovea (cilioretinal artery patent), retinal whitening, arterial attenuation, cattle tracking (emboli), ONH oedema (think of AION).
- Rule out GCA – FBC / ESR / CRP / Temporal artery biopsy / steroids Rx.
- Carotid Doppler USS
- Referral to TIA clinic
- Young patients – hypercoagulable cause – blood test for homocysteine, sickle cell, Factor V Leiden, protein C & S, antithrombin III and antiphospholipid antibody.
- Conservative treatment
- Active treatment – window of 4 hours (irreversible damage after onset – retina can withstand ischaemia without damage up to 97 minutes after onset of CRAO) – ocular massage or AC paracentesis to dislodge emboli.