Incidence of hypoperfusion retinopathy is twice as high in males as it is in females due to a higher prevalence of cardiovascular disease.7 Hypoperfusion retinopathy rarely presents before the age of 50 years, with the average age of onset around 65 years.7 The exact rate of occurrence is unknown as this condition often is underdiagnosed because it mimics other vascular conditions, such as venous occlusive disease and diabetic retinopathy.1,7 Patients can present asymptomatically where findings are incidental on a dilated eye exam, or they may present with vision loss that can be gradual, sudden, or transient in nature.5,6,8
Gradual vision loss can follow a period of weeks to months and can occur secondary to posterior ischemia, macular edema, or choroidal hypoperfusion.1,3,8,9 Sudden vision loss can occur from severe hypoperfusion, creating an acute inner layer retinal ischemia. This type of vision loss often is accompanied by a cherry red spot in the macula and can be caused by an embolic plaque.1,8 Transient vision loss (TVL) also can be secondary to a plaque emboli or light induced. Patients with light-induced TVL report poor to blurry vision or prolonged after image when exposed to bright lights. In theory when the retina is exposed to light, there is an increase in metabolic demand that is unmet in those with choroidal vascular insufficiency from significant carotid stenosis.3,8,10
The clinical presentation most often is unilateral. Early stages of the disease generally affect the midperipheral retina but can be found in the posterior pole with chronicity. Early findings include microaneurysms, nerve fiber layer and inner retinal layer hemorrhages, and dilated, but generally not tortuous, veins.5 Chronic stage findings include arteriolar narrowing, extreme venous dilation, occasionally macular edema, and neovascularization of the disc and or retina.5 Disc edema or collaterals usually are not present.5
The mechanism behind hypoperfusion retinopathy results from an overall ischemic cascade and starts with comorbid cardiovascular conditions, such as hypertension, hypercholesterolemia, diabetes, heart disease, and history of smoking.1,2,5 These conditions play a role in creating atherosclerotic buildup in the arterial lumen leading to chronic narrowing and a decrease in arterial perfusion pressure. Over time, a low-grade hypoxic situation is formed, generating vascular endothelial cell damage and pericytes cell loss, thus causing leakage of fluid.1,2,5 With these chronic hypoxic states, angiogenic factor release eventually leads to posterior neovascularization.1,2,5 Further chronicity of carotid occlusive disease can create a panocular ischemia that also involves anterior structures, including iris, conjunctiva, episclera, or cornea. At this point, hypoperfusion retinopathy progresses to a more severe condition called ocular ischemic syndrome (OIS).2,5
Ocular ischemic syndrome can be associated with a 40% mortality rate within 5 years of onset as it is generally found in those with overall poor health.5 Along with posterior neovascularization, anterior structures also are involved. Sixty-seven percent of cases have iris or angle neovascularization of which 35% go on to develop neovascular glaucoma and its complications.1,8 With OIS, 90% of cases have some type of vision loss, and 40% report ipsilateral ocular pain.1,8 Visual loss can be gradual, sudden, or transient. The pain can occur from ocular ischemia, ruptured corneal epithelial microcysts secondary to acute glaucoma, elevated intraocular pressure (IOP) with neovascular glaucoma, or from ipsilateral dural ischemia.1,5,6,8 Fluorescein angiography is commonly used to diagnose and manage OIS, because it allows for the visualization of retinal and choroidal circulation and the detection of neovascular proliferation and ischemic areas.
Diagnostic Imaging
Several diagnostic testing strategies are available to evaluate for carotid occlusive disease. Carotid ultrasonography is a noninvasive, safe, and inexpensive screening tool to evaluate for high-grade stenosis. However, it can sometimes overestimate the degree of stenosis and is not reliable with severe calcifications.8 Computed tomography angiography and magnetic resonance angiography are minimally invasive tools that can be used to screen or confirm the degree of stenosis.8 These can be used in addition or instead of ultrasonography, especially in instances where patients have a short neck or high carotid bifurcation that may affect reliability. Both are contraindicated in those with renal failure as both modalities require the use of a contrast dye. Magnetic resonance angiography is far more expensive, time consuming, and not readily available.8 Carotid angiography is considered the gold standard for imaging the entire carotid artery system because it allows for the evaluation of plaque morphology, atherosclerotic disease, and collateral circulations.8 The disadvantages to this invasive and high-cost procedure include a risk of mortality that can occur secondary to an embolic stroke, myocardial infarction (MI), carotid artery dissection, or arterial thrombosis.8
Treatment
Treatment and management for carotid artery stenosis is focused on combined effort with the patient’s PCP and other specialists, including cardiologist, neurologist, and vascular surgeons.11 Treatment of comorbid conditions, education on healthy lifestyle, and smoking cessation are all imperative to the patient’s well-being. Managing ocular sequelae is based on specific findings and can include intravitreal antivascular edothelial growth factor or steroidal injections, pan retinal photocoagulation, or hypotensive drops.6,7