Ocular Ischemic Syndrome: A Case of Radiation-Induced Carotid Stenosis | Healio

A 65-year-old woman presented with nine months of intermittent “kaleidoscopic” visual disturbances and blurred vision, most noticeable upon awakening. This case, detailed in Ocular Surgery News, highlights the importance of considering ocular ischemic syndrome (OIS) in patients with significant cardiovascular risk factors, even when initial eye exams appear relatively normal.

The patient’s medical history is extensive, including hypertension, hyperlipidemia, a prior transient ischemic attack, peripheral arterial disease, bilateral ischemic strokes, postural hypotension, a history of carotid artery stenosis treated with stenting, papillary thyroid carcinoma treated with radical neck dissection and radiation, and breast cancer treated with lumpectomy and radiation. She was taking multiple medications, including clopidogrel, levothyroxine, and atorvastatin. Her ocular history included migraines and cataracts, but no prior ocular procedures or current ophthalmic medications.

Understanding Ocular Ischemic Syndrome

Ocular ischemic syndrome is a relatively uncommon but potentially vision-threatening condition caused by chronic reduced blood flow to the eye. It most often stems from severe carotid artery disease, though other vascular issues can contribute. The syndrome typically affects older individuals with pre-existing atherosclerotic risk factors, like those present in this patient’s case. Symptoms can vary, ranging from gradual or intermittent vision loss to flashes of light (photopsias) and eye pain. These disturbances are often worse in the morning or when blood pressure is lower.

Early signs can be subtle. Even as some patients develop obvious retinal hemorrhages or neovascularization (abnormal blood vessel growth), others may have minimal findings on a standard eye exam. This makes a high degree of clinical suspicion crucial, particularly in individuals with a history of vascular disease. As the condition progresses, more pronounced signs like optic nerve pallor or retinal vessel abnormalities may become apparent.

Diagnostic Evaluation

The patient underwent a comprehensive ophthalmic examination. Visual acuity was 20/20 in both eyes, and intraocular pressure (IOP) was within normal limits. Pupils reacted normally, and there was no evidence of optic nerve swelling or damage. The front portion of the eye appeared normal, with only minor epithelial erosions and early cataracts. However, fundus autofluorescence imaging and optical coherence tomography (OCT) revealed subtle changes, and fluorescein angiography showed delayed blood flow to the retina.

Fluorescein angiography, a diagnostic test where dye is injected into a vein to visualize blood flow in the retina, was particularly informative. It demonstrated prolonged transit times in both eyes, indicating reduced blood flow, but no evidence of widespread retinal ischemia. This finding, combined with the patient’s vascular history, strongly suggested OIS. You can learn more about fluorescein angiography from the American Academy of Ophthalmology.

The Role of Radiation Therapy

A key aspect of this case is the patient’s extensive history of radiation therapy. She received radiation for papillary thyroid carcinoma as a teenager and again for breast cancer decades later. Radiation exposure is known to damage blood vessels, leading to inflammation and fibrosis (scarring) of the carotid arteries. This accelerates the development of atherosclerosis and stenosis (narrowing of the arteries), increasing the risk of OIS. Research published in JACC Basic Transl Sci highlights the link between radiation and vascular damage.

Differential Diagnosis and Ruling Out Other Conditions

It’s important to differentiate OIS from other conditions that can cause similar symptoms. These include diabetic retinopathy, central retinal vein occlusion, retinal artery occlusion, and inflammatory vasculopathies like giant cell arteritis. Migraine-associated visual disturbances and transient ischemic attacks can also mimic OIS. The patient’s detailed medical history and the results of the diagnostic tests helped to rule out these other possibilities.

Management and Next Steps

The evaluation of suspected OIS requires a combined approach, involving both an ophthalmologist and a vascular specialist. In this case, the patient was referred for further cardiovascular evaluation, including carotid artery imaging, to assess the extent of her vascular disease. Ophthalmologic management focuses on treating any complications of chronic hypoperfusion, such as neovascularization of the iris or angle, which can lead to glaucoma. Panretinal photocoagulation and intravitreal anti-VEGF therapy may be used to manage these complications.

Two months after the initial presentation, the patient’s condition was re-evaluated. While her visual acuity remained stable, fundus examination revealed minor hemorrhages in both eyes. OCT angiography showed an enlarged foveal avascular zone in the right eye, but no evidence of neovascularization. She will continue to be monitored closely for any signs of worsening ischemia.

This case underscores the importance of considering OIS in patients with a history of vascular disease, even when initial eye exams are unremarkable. Early diagnosis and management can help to prevent vision loss and improve overall cardiovascular health. Further research is needed to better understand the long-term effects of radiation therapy on vascular health and the optimal strategies for preventing and treating OIS in these patients.

For more information, consult with a qualified ophthalmologist or vascular specialist. You can also find additional resources from the National Eye Institute.