What is Ocular Ischemic Syndrome?

Ocular ischemic syndrome (OIS) is a condition caused by significantly decreased blood flow to the eye and orbit due to the narrowing or blockage of the internal carotid arteries. With an estimated 7.5 cases per year per million people, OIS is very rare, but its complications may lead to irreversible vision loss.

The carotid arteries send blood to your brain after branching off from the aorta artery, which is the main artery transporting blood out of the heart. You have two carotid arteries; one is internal, and the other is external, the one where you can feel your pulse in the neck. The primary blood source to the eye and orbital structures is the ophthalmic artery which branches out from the internal carotid artery.

The primary cause of OIS

Atherosclerosis is the primary cause of blockage in the carotid arteries. Atherosclerosis is a disease where a buildup of fats, cholesterol, and other elements, called plaque, builds up inside your arteries. As time goes on, the plaque will harden and narrow the arteries leading to lowered ocular blood flow called hypo-perfusion. Occlusion can lead to rapid death of retinal cells resulting in severe loss of vision.

Most OIS patients have a narrowing of 90% or more of the carotid artery; a few do not. Conversely, not all patients with significant carotid artery occlusion have OIS.

Demographics and incidence

Ocular ischemic syndrome commonly occurs in elderly patients at an average age of 65, but OIS is rare before age 50. OIS is more common in men than women due to the higher incidence of atherosclerosis and carotid artery disease in male patients. The incidence of ocular ischemic syndrome is not race-related.

OIS Symptoms

Hypo-perfusion can produce a range of symptoms depending on the severity of the compromised arteries. The main symptoms are visual impairment, ocular pain, and other visual defects.

Visual impairment – Visual loss in the affected eye is present in over 90% of OIS patients. It is usually related to chronic or acute retinal ischemia or damage to the optic nerve due to secondary glaucoma. 

In 67% of patient’s visual loss occurs gradually over a few weeks or months. In 12%, it occurs over a period of days, and in another 12%, the loss is sudden over a period of minutes or seconds. In patients with a sudden visual loss, a cherry-red spot is usually observed at the fundus related to the central retinal artery’s blood flow stoppage.

Ocular Pain – Pain in the affected eye or the periorbital area may be present in 40% of patients and is usually due to neovascular glaucoma. Still, in patients with normal intraocular pressure (IOP), it may be caused by hypoxia (oxygen deprivation) of the eyeball. Ischemic pain is described as dull; it develops gradually over hours or days and is relieved when the patient lies down.

Other Visual Defects – Another symptom is transient visual loss, a temporary sudden total or partial visual loss lasting from seconds to minutes. Transient visual loss occurs in about 10% of OIS patients, but most patients with this symptom do not have OIS.

Diagnosis of Ocular ischemic syndrome

One test regularly used to diagnose OIS is fluorescein angiography. The ophthalmologist or retinal specialist injects a fluorescent dye into the bloodstream that allows blood vessels to be photographed in the back of the eye.

The carotid artery imaging helps to see if the retina and choroid blood vessels are getting adequate blood flow and establish a diagnosis of ocular ischemic syndrome. By timing the circulation time and normal retinal filling time of the fluorescent dye, which is about five seconds normally, it may take one minute or more in an affected eye, indicating severe hypoperfusion (decreased blood flow).

The diagnosis procedure provides a differential diagnosis to determine if it may not be OIS but conditions with similar signs or symptoms with other retinal vascular diseases. Conditions such as diabetic retinopathy or central retinal vein occlusion may be the correct diagnosis and require different treatment. In OIS, intra-retinal hemorrhages are fewer than diabetic retinopathy, for example.

Management & Treatment of Ocular Ischemic Syndrome

With prompt and proper treatment, OIS patients have options.

The ocular ischemic syndrome results from atherosclerosis plaque clogging the blood vessels that provide blood to the eyes. Treatment of OIS often requires a multidisciplinary approach. Treatments may include:

  • Surgery called carotid endarterectomy (CEA) to remove blockages to the normal flow of blood.
  • Blood thinners followed by intravitreal injections of a medication directly into the space in the back of the eye called the vitreous cavity.
  • Pan retinal photocoagulation, also known as PRP or scatter laser treatment, is a minimally invasive laser procedure used to seal or destroy leaking blood vessels on the retina. However, PRP is effective in only 35% of eyes since choroidal ischemia, which plays an important role in developing neovascularization, is unaffected by laser photocoagulation.

Warning signs

Ocular ischemic syndrome may be a warning sign of an impending stroke, or retinal artery occlusion, a stroke of the eye. Because OIS is connected with atherosclerosis, patients typically have other related chronic diseases or conditions. 73% of the patients have hypertension (high blood pressure), and 56% have diabetes. The mortality rate is as high as 40% within five years of onset.

Cardiovascular disease is the main cause of death (approximately 66%), followed by stroke as the second leading cause of death, which is why patients with OIS should be referred to the cardiologist for imaging studies of the carotid arteries and the vascular surgeon.

Considering that signs of severe carotid artery stenosis may be first observed in the eye before they are manifested in the cerebrovascular system, the ophthalmologist has a significant role in the proper diagnosis and referral for further investigations. Collaboration between the ophthalmologist, vascular surgeon, cardiologist, neurologist, and primary care physician is essential for the OIS patient’s appropriate management.

Contact Arizona Retinal Specialist

If you are experiencing any Ocular ischemic syndrome symptoms or have cardiovascular disease, please contact us immediately and schedule an appointment. As mentioned previously, OIS is a rare disease, and you may just be experiencing symptoms of other eye conditions. We can give you a comprehensive eye exam and help to make sure your vision remains healthy. Call 623 – 474 – 3937 (EYES) now!


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