Ocular Ischemic Syndrome (OIS)

Description

Ocular Ischemic Syndrome (OIS) arises due to a chronic and severe impairment of the arterial circulation to the eye. The most common cause of ophthalmic artery hypoperfusion is carotid artery stenosis (carotid occlusive disease). Less common causes include arteritis (e.g., giant cell arteritis, Takayasu’s arteritis and syphilis), collagen vascular disease and carotid dissection. OIS tends to be unilateral or asymmetric, and the ipsilateral internal carotid artery must have 80% to 90% stenosis before a marked lowering of the retinal arterial perfusion pressure becomes apparent. OIS is often associated with cerebrovascular or ischemic heart disease, and in conjunction with diabetes.

Symptoms

Loss of vision usually develops in one eye over a period of weeks to months. A dull ache in and around the eye is common. The patient may have experienced temporary obscurations of vision (amaurosis fugax), transient ischemic attacks or strokes. Symptoms of systemic inflammatory conditions include fatigue, weight loss, arthralgias, myalgias, and headaches.

Signs

Unilateral or asymmetric signs of widespread ocular ischemia:

(a) Posterior segment – retinal capillary walls become incompetent, resulting in microaneurysms and dot haemorrhages. Dilated (but not tortuous) retinal veins, attenuated arterioles, optic disc and retinal neovascularization, cotton wool spots and generalized retinal pallor.

(b) Anterior signs: Typically, the eye is red, with injection of conjunctival and episcleral vessels. Corneal edema and aqueous flare are common. Iris neovascularization (rubeosis iridis) is characteristic, occurring in two-thirds of cases. Cataract is also common, and may develop rapidly.

(c) Neovascular glaucoma may be present, with raised intraocular pressure (IOP) and iridocorneal angle changes.

Incidence

This is a rare condition (approximately 1 per 100,000), at least partly because the blood supply to the eye is protected by numerous anastomoses between the internal and external carotid arteries.

Significance

Ophthalmic artery hypoperfusion often reflects more generalized atherosclerosis that may be potentially life threatening, e.g., the risk of stroke or heart attack.

Differential Diagnosis

Diabetic retinopathy, Central retinal vein occlusion, Venous stasis retinopathy, Hypertensive retinopathy, Systemic Lupus Erythematosis.

See Also

Amaurosis Fugax, Neovascular Glaucoma, Cataract, Arteritic Ischaemic Optic Neuropathy, Nonarteritic Ischaemic Optic Neuropathy.

Management

The principal aims of treatment are to limit further loss of vision and treat the systemic pathology.

Blood Tests

Immediate erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are indicated to exclude giant cell arteritis in patients over 60 years of age. Carotid Doppler ultrasonography is recommended. Fasting blood glucose, lipid studies, and a coagulation profile are indicated in the risk assessment of atherosclerosic disease. A vasculitic screen may also be indicated, especially in patients under 60 years of age or with suggestive clinical features.

Ocular Investigations

Fluorescein angiography is useful to confirm OIS: signs include delayed and patchy choroidal filling, prolonged arteriovenous transit time and arteriolar staining. Ultrasound studies (e.g., orbital colour Doppler imaging) may be used to measure ocular perfusion and blood vessel flow velocities. Formal ophthalmodynamometry is useful when central retinal vein occlusion (CRVO) cannot be excluded: ocular perfusion pressure is low in carotid disease, but normal to increased in CRVO.

Laser surgery

Panretinal laser photocoagulation may be beneficial in the presence of neovascularisation, although there is minimal evidence to support this practice.

Topical medication

Ocular hypotensive medications may be indicated for glaucoma or to improve ocular perfusion.

Incisional surgery

In patients with symptomatic, severe (greater than 70%, but not 100%) carotid artery stenosis, carotid endarterectomy has been shown in prospective, controlled, randomised trials to substantially reduce the risk of stroke (North American Symptomatic Carotid Endarterectomy Trial; European Carotid Surgery Trial).

Review and prognosis

Occasionally, treatment of carotid artery stenosis improves ciliary body perfusion, resulting in increased aqueous formation and increased IOP. Attentive monitoring of IOP is therefore required after carotid surgery. Specialized assessment and management of systemic vascular disease will be necessary, since there is a significant risk of mortality due to cardiovascular disease or stroke.