Ocular Ischaemic Syndrome

Ocular ischaemic syndrome (OIS) is ocular hypoperfusion caused by severe stenosis or occlusion of the internal or common carotid artery (usually over 90 percent stenosis), or rarely the ophthalmic artery, from atherosclerosis (commonest), giant cell arteritis, Takayasu disease, aortic arch disease or dissection.

• Age 50 to 80 years; men more than women (2:1); incidence about 7.5 per million per year.
• Risk factors: hypertension, diabetes, hyperlipidaemia, smoking, coronary and peripheral vascular disease.
• Associated with high cardiovascular mortality: 5-year mortality about 40 percent (mostly from cardiac events and stroke).
• Anterior segment ischaemia, reduced aqueous production (lowers pressure despite neovascular angle closure), and posterior segment ischaemia.

• Visual loss (gradual in 60 percent, sudden in some), amaurosis fugax, prolonged recovery after exposure to bright light (more than 1 minute), and dull orbital ache relieved by lying down (ocular angina).
• Anterior segment: rubeosis iridis, neovascular glaucoma (but intraocular pressure may be normal or low because of ciliary hypoperfusion), anterior chamber flare without cells, cataract, corneal oedema, hypotony.
• Posterior segment: dilated but non-tortuous retinal veins, mid-peripheral dot and blot haemorrhages, microaneurysms, cotton wool spots, neovascularisation of the disc or elsewhere (35 percent), spontaneous retinal arterial pulsation, cherry red spot (embolic occlusion).
• Attenuated retinal arteries, macular oedema, and optic neuropathy.

• Ophthalmic examination with undilated gonioscopy and dilated fundus examination; ophthalmodynamometry or digital pressure on the globe causing spontaneous arterial pulsation.
• Fluorescein angiography: delayed choroidal filling (over 5 seconds), prolonged arteriovenous transit (over 11 seconds), peripheral non-perfusion, vessel staining and leakage.
• Carotid duplex ultrasound, CT or MR angiography of the neck vessels to define stenosis; echocardiography and ECG.
• Exclude giant cell arteritis (ESR, CRP, temporal artery biopsy) in older patients; blood tests for glucose, HbA1c and lipids.
• Differentiate from central retinal vein occlusion (tortuous veins, flame haemorrhages) and diabetic retinopathy (usually bilateral).

• Urgent vascular referral and secondary stroke prevention:
  • Carotid endarterectomy or stenting for symptomatic stenosis of 70 to 99 percent (and selected 50 to 69 percent), ideally within 2 weeks of symptoms; revascularisation can stabilise or improve vision when done early, but may fail to improve established neovascular glaucoma.
  • Antiplatelet therapy: aspirin 75 to 100 mg daily, with clopidogrel 75 mg daily (loading 300 mg) for 21 to 90 days after a minor event; high intensity statin (atorvastatin 40 to 80 mg daily), blood pressure control (avoid excessive lowering because it can reduce ocular perfusion), glycaemic control, smoking cessation.
• Ocular treatment:
  • Panretinal photocoagulation for retinal or iris neovascularisation, and intravitreal anti-VEGF (bevacizumab 1.25 mg or aflibercept 2 mg) to induce rapid regression.
  • Neovascular glaucoma: topical pressure lowering agents (low baseline aqueous production, so use caution) with atropine 1 percent and prednisolone acetate 1 percent for inflammation and pain; drainage device or cyclophotocoagulation if needed.
  • Macular oedema: anti-VEGF or intravitreal steroid.
• Monitor every 1 to 3 months initially.
• Cardiovascular screening: coronary and peripheral vascular assessment, and treatment of risk factors.