What Is Ocular Ischemic Syndrome

If you have suffered a stroke or are diagnosed with a carotid artery disease, you may be at risk of experiencing ocular ischemic syndrome (OIS). This is a rare eye condition that could be harmful to your vision.

Ocular ischemic syndrome occurs due to insufficient blood flow to the eyes, caused by plaque accumulation blocking the carotid arteries in your neck, or caused by the blood vessels that conduct blood to your eyes becoming narrow. Consequently, you experience pain and vision loss.

This article will focus on explaining the causes and symptoms of this condition, how physicians diagnose it, the available treatments and possible prevention methods. So if you want a better understanding of this problem, keep reading.

What causes ocular ischemic syndrome?

Here are the main causes behind OIS:¹

• Carotid artery disease: your artery walls become thicker due to a buildup of plaque, which are sticky deposits of cholesterol, proteins, cells, and calcium. As a consequence of this narrowing, the blood has less space to flow, and the ocular blood vessels, which branch out from the carotid arteries in the neck, supply less blood to the eyes, leading to ocular ischemic syndrome.
• Atherosclerosis: this is the plaque accumulation in your artery walls. It is a major cause of OIS. This blockage of your blood vessels reduces blood supply, resulting in ischemia, which is a lack of oxygen and glucose in your eyes.

Other potential causes include the following, as well as coexisting conditions:²

• Carotid artery dissection
• Giant cell arteritis
• Takayasu arteritis
• Behcet’s disease
• Fibromuscular dysplasia
• Hypertension
• Diabetes
• Heart attack

What are the symptoms of ocular ischemic syndrome?

The most common symptom of ocular ischemic syndrome is visual loss. Other clinical manifestations can appear as:²

• Appearance of abnormal blood vessels on the iris
• Neovascular glaucoma
• Inflammation of the eye
• Synechia
• Spontaneous haemorrhages in the eye
• Asymmetric cataract
• Sensitivity to light
• Redness
• Corneal swelling
• Narrowed blood vessels in the retina
• Retinal telangiectasia
• Spontaneous retinal artery pulsations
• Microaneurysms
• Patches on the retina and the macula
• Paralysis or weakness of the eye muscle
• Eye pain
• Pain caused by elevated intraocular pressure
• Droopy eyelid
• Neovascularisation
• Ischemic optic neuropathy

How is ocular ischemic syndrome diagnosed?

To accurately diagnose ocular ischemic syndrome, experts also test for diabetic retinopathy and central retinal vein occlusion (CRVO), to discard them, as they present similar symptoms. The table below shows how OIS is differentiated from other health issues.²

Depending on whether you visit an ophthalmologist or a cardiologist, these experts will order the following tests:¹

An eye-expert will look at:

• Fluorescein angiogram: looks at your blood vessels, in particular, to check how long it takes for the blood to reach the vessels in your eyes, and if there is any leakage
• Indocyanine green angiography (ICG): similar to a fluorescein angiogram, but provides more accurate information
• Electroretinogram (ERG): tests how the retina responds to light stimuli
• Visual-evoked potentials (VEP): measure how the visual cortex responds to visual stimuli
• Ophthalmodynamometry: measures intraocular pressure

Cardiologists will ask for tests that evaluate carotid occlusive disease:

• Colour doppler imaging of retrobulbar vessels: displays the direction and speed of blood in vessels. This helps identify narrowed arteries 
• Carotid duplex ultrasound: shows narrowed and blocked arteries
• Magnetic resonance angiography (MRA) and Computed tomographic angiography (CTA): show more accurate information on blood vessel state and blood flow
• Carotid arteriography: presents the state of blood vessels in the neck and head. However, it is rarely used, and only in specific cases

How is ocular ischemic syndrome treated?

Treating ocular ischemic syndrome is a multidisciplinary approach that targets ocular issues, cardiovascular problems, and any other coexisting conditions. 

Ocular treatments

Ocular treatments include:^1,2

• Medications like β (beta) blockers and α-2 (alpha) agonists are used to decrease intraocular pressure
• Steroids and anti-vascular endothelial growth factor (anti-VEGF) are used to treat retinal inflammation, as well as control vascularisation in the eye
• Surgery relieves intraocular pressure and pain and is recommended before neovascularisation occurs

Cardiovascular (carotid artery condition) treatments

Carotid artery disease treatments include:^1,2

• Carotid artery endarterectomy (CEA): this surgery aims to remove the plaque formation in your carotid artery, facilitating blood circulation to the eyes
• Carotid artery stenting (CAS): this surgical procedure inserts a special tube into your obstructed carotid artery, and it compresses the plaque formation against the vessel walls, opening the artery, and restoring blood flow to the eye
• Bypass Surgery: this procedure creates a new path for the blood to travel to the eyes

Systemic treatments

Patients with ocular ischemic syndrome often suffer from other coexisting conditions, hence, they need to be evaluated by their general practitioner, and treated appropriately. This type of treatment can include:^1,2 

• Medications that prevent plaques from forming, for example, antiplatelet drugs
• Medications that treat diabetes, atherosclerosis, and coronary heart disease
• Medications that reduce hypertension
• Changes in diet
• Exercise
• Stopping smoking

What is the prognosis for ocular ischemic syndrome?

This condition usually affects older individuals, between 50 and 80 years old. Moreover, assigned males at birth (AMAB) are more affected than assigned females at birth (AFAB), due to a higher occurrence of cardiovascular issues. Additionally, in 80% of the cases, only one eye is affected.²

What is more, the mortality rate after 5 years is 40%, meaning that 40 in 100 individuals will die within the first five years of being diagnosed. The major cause of death in this case is myocardial infarction.¹

Regarding vision, within the first year of diagnosis, 50% of patients show a decreased visual acuity. Furthermore, patients who experience neovascularisation suffer visual loss after three months.¹

What are the complications?

While the most obvious complication is vision loss, there are some other issues that you could experience before this. As OIS progresses, you might develop neovascular glaucoma, a secondary type of glaucoma where the area between your iris and cornea is obstructed by abnormal blood vessels. If this happens, you might also experience ischemic optic neuropathy, eye haemorrhage, eye muscle paralysis, swelling in your eyes, and altered ocular pressure.¹

How can you prevent ocular ischemic syndrome?

There are certain lifestyle modifications you could adopt to prevent carotid artery disease and ocular ischemic syndrome from developing, like:

• Having a well-balanced diet, like a Mediterranean diet, rich in fruits, vegetables, legumes, whole grains, fishy oils, and moderate in red meats, saturated fats, and dairy consumption can reduce the risk of cardiovascular issues³
• Regular exercising is good for your cardiovascular health, as it may reduce blood pressure, and therefore, intraocular pressure. However, you should find a physical activity that adapts to your needs, and if you suffer from a heart problem you should consult a cardiologist
• If you have other coexisting conditions, like diabetes, hypertension, or other cardiovascular issues try to monitor them. You can do so by having constant medical check-ups, taking your medications, and consulting your physician if you believe there might be something wrong
• Visit an ophthalmologist and get eye examinations frequently. This could mean an early detection of OIS and would allow an early intervention, which could prevent irreversible damage
• Quit smoking
• Achieve and maintain a weight which is healthy for you. This will vary from person to person

Summary

Ocular ischemic syndrome is a harmful eye problem which could potentially lead to vision loss. The main cause of this is the obstruction of the carotid arteries in the neck, by plaque accumulation. As a result, the blood vessels narrow and the blood might have difficulties flowing to the eyes. Some physical displays of this problem might include increased intraocular pressure, eye inflammation, neovascularisation, appearance of patches in different areas of the eye, and loss of vision. For a differential diagnosis of OIS, experts also need to test for diabetic retinopathy and CRVO. Moreover, depending if you visit an ophthalmologist or a cardiologist, different examinations will be performed. Since the treatment for this problem consists of a multidisciplinary approach involving ocular, cardiovascular and systemic treatment, it is important for healthcare professionals to collaborate to minimise patients' damage and mortality.