Ocular ischemic syndrome

Overview

Ocular ischemic syndrome (OIS) is a rare but serious vision-threatening condition caused by chronic hypoperfusion (reduced blood flow) of the eye. It results from significant obstruction of the carotid arteries, particularly the internal carotid artery, which impairs blood supply to the ophthalmic artery and its branches. OIS primarily affects middle-aged to elderly individuals and is often associated with widespread atherosclerotic disease. Because the symptoms can mimic other ocular conditions, OIS is frequently underdiagnosed, and early recognition is essential to prevent irreversible visual loss and life-threatening cerebrovascular events.

Causes

The most common cause of ocular ischemic syndrome is severe carotid artery stenosis or occlusion, typically due to atherosclerosis. Less common causes include:

• Carotid artery dissection

• Giant cell arteritis

• Thromboembolism

• Radiation-induced vasculopathy

• Cardiogenic emboli

In most cases, the affected carotid artery is narrowed by 90% or more. This leads to insufficient perfusion of the eye and orbit, especially during periods of increased demand or reduced systemic blood pressure.

Symptoms

Ocular ischemic syndrome typically presents with both visual and ocular symptoms, often affecting one eye. The condition develops gradually, although some symptoms can appear acutely. Common symptoms include:

• Visual loss: Gradual, painless, and progressive vision loss in one eye. It may be sudden in rare cases.

• Amaurosis fugax: Transient episodes of vision loss or "curtain falling" over the eye.

• Ocular pain: Dull, aching pain around the eye, often worse in dim lighting due to pupil dilation increasing oxygen demand.

• Photophobia: Increased sensitivity to light.

• Prolonged recovery of vision after light exposure

On examination, signs may include:

• Rubeosis iridis: Abnormal new blood vessels on the iris surface.

• Anterior segment inflammation: Mild cells and flare in the anterior chamber.

• Retinal hemorrhages: Particularly in the mid-peripheral retina.

• Microaneurysms, cotton-wool spots, and dilated retinal veins

• Neovascular glaucoma: Secondary to neovascularization of the angle structures.

Diagnosis

Diagnosis of ocular ischemic syndrome requires a combination of clinical evaluation, imaging studies, and vascular assessment. Key diagnostic methods include:

• Ophthalmologic examination: Slit-lamp biomicroscopy and dilated fundus examination reveal characteristic retinal and iris changes.

• Fluorescein angiography: Shows delayed choroidal filling, prolonged arteriovenous transit time, and patchy retinal capillary perfusion.

• Carotid Doppler ultrasonography: Evaluates the degree of carotid artery stenosis.

• CT angiography or MR angiography: Provides detailed imaging of carotid and cerebral vasculature.

• Ocular pulse amplitude measurement: May reveal reduced ocular blood flow.

• Electroretinography (ERG): Shows reduced amplitude of both a- and b-waves in ischemic retina.

Treatment

Treatment of ocular ischemic syndrome involves both ocular management and addressing the underlying vascular cause. A multidisciplinary approach involving ophthalmologists, neurologists, and vascular surgeons is often necessary.

Systemic/Vascular Management

• Carotid endarterectomy: Surgical removal of atherosclerotic plaque in cases of severe carotid stenosis.

• Carotid artery stenting: An alternative to endarterectomy, especially in high-risk surgical patients.

• Medical management: Includes antiplatelet therapy, statins, blood pressure control, and diabetes management.

Ocular Management

• Panretinal photocoagulation (PRP): To manage neovascularization and reduce the risk of neovascular glaucoma.

• Intravitreal anti-VEGF injections: Used to control neovascularization in the iris and retina.

• Management of glaucoma: Includes topical and systemic intraocular pressure-lowering medications, and in advanced cases, surgical intervention.

Prognosis

The visual prognosis in ocular ischemic syndrome is generally poor, especially if treatment is delayed. Over 90% of patients present with vision worse than 20/60, and more than half may be legally blind in the affected eye. The presence of neovascular glaucoma further worsens outcomes.

Systemically, the prognosis is also guarded due to the underlying carotid artery disease. Patients with OIS have a high risk of stroke, myocardial infarction, and death. Prompt recognition and vascular intervention can reduce these risks and stabilize ocular findings, although visual recovery is often limited. Lifelong follow-up with both ophthalmic and cardiovascular care is essential.