PLAY A ROLE IN STROKE PREVENTION BY IDENTIFYING VISUAL DISTURBANCES

STROKE, OR cerebrovascular accident, is a leading cause of death and disability in the U.S. In fact, stroke kills about 140,000 Americans each year — that’s one out of every 20 deaths, according to the CDC. More alarming? Someone in the United States has a stroke every 40 seconds, while every four minutes, someone dies of a stroke.

The good news: About 80% of strokes are preventable. We, as eye care providers, can play a role in stroke prevention by identifying visual disturbances, such as transient ischemic attacks (TIA), and identifying certain retinal vascular changes — both of which are strong indicators of stroke risk.

Here, I provide an overview of stroke, TIAs and retinal signs of stroke, the imaging devices to aid you in identifying them and the stroke management protocol.

STROKE OVERVIEW

A stroke is caused by an interruption in blood flow through the brain. Strokes may be ischemic, hemorrhagic or TIA.

Ischemic strokes, which account for a majority (about 87%) of all strokes, occur when a blood vessel is obstructed by a blood clot or embolus.

Hemorrhagic strokes stem from the rupture of a blood vessel or aneurysm in the brain. Specifically, an intracerebral bleed occurs within the brain, while a subarachnoid hemorrhage involves rupture of an artery between the surface of the brain and skull. This bleeding is often signaled by a sudden, severe headache.

A TIA, or mini-stroke, is considered by some a subtype of ischemic stroke. It is a temporary disruption of blood flow to the brain that produces symptoms, including vision loss, which usually lasts less than five minutes, with no permanent damage. A TIA is both a warning of an impending stroke and an opportunity to take steps to prevent it.

A primary red flag for stroke is high blood pressure, the single most important treatable risk factor. About three in every four people (77%) who have a first stroke have high blood pressure, states the American Heart Association.

Nearly half of U.S. adults (46%), up from 32%, could be classified with high blood pressure, under the American College of Cardiology/American Heart Association 2017 guidelines (130/80 rather than 140/90), according to Hypertension. High blood pressure should be treated early with lifestyle changes and, in patients who make lifestyle changes but still have high blood pressure, medication.

Yet, many patients are unaware they have high blood pressure and, of those who are aware, only about half have it under control, according to the CDC. Given this information, it may be worth considering purchasing a sphygmomanometer to routinely check blood pressure, as some patients may see their eye care provider more than their primary care provider, and you could alert them to their risk of stroke.

SIGNS OF STROKE

TIAs can result in blurry vision, transient monocular blindness (amaurosis fugax) or VF deficits in one or both eyes that occur rapidly and resolve in a few minutes. Up to 50% of TIAs, including brief attacks (minutes), have been shown to be associated with infarction on MRI of the brain, and an acute ischemic stroke requires emergent treatment, reports the Practical Neurology Journal. In fact, the 2017 Clinical Guidelines for Stroke Management state that all patients who have suspected TIAs be assessed urgently.

Hypertensive retinopathy (HTR) is a stroke risk. Specifically, there is a two-fold increase incidence of stroke in patients who have mild HTR, focal arteriolar narrowing or arteriovenous (A/V) nicking, reports the Atherosclerosis Risk in Communities study. Patients who have moderate disease, retinal or flame-shaped hemorrhages and cotton wool spots, or severe retinopathy were up to three times more likely to develop a stroke, the study reveals.

Retinal vascular occlusions (RAO) (veins or arteries) are associated with an increased risk of developing stroke as well. A study in the American Journal of Ophthalmology shows that 24.2% of patients with RAO had concurrent acute brain ischemia. Alarmingly, 37.5% did not present with any neurologic symptoms or findings. The current recommendation for acute RAOs, specifically central or ophthalmic, is emergent stroke evaluation, states the AAO Preferred Practice Patterns 2016.

Also, patients with retinal vein occlusions have an almost two-fold greater risk for stroke, states Archives of Ophthalmology.

Retinal emboli is another ocular sign that may precede stroke. In fact, there was a 10-fold increase in the rate of stroke in patients with retinal emboli, reports a study in Stroke Journal.

Finally, ocular ischemic syndrome can indicate carotid artery disease and, thus, may be associated with a higher risk of stroke development.

IMAGING DEVICES

Although MRI is a powerful tool in the diagnosis of stroke, retinal signs should not be neglected. These devices can aid you in both the diagnosis and management of stroke warning signs.

• VF Testing. Routinely performed post-stroke, this can detect TIA-related visual disturbances, such as scotomas or homonymous hemianopia VF deficits.
• Fundus photography. Retinal photography of vasculature changes, such as early HTR changes (A/V nicking), aids in the assessment of stroke risk. Plus, it is an excellent means of monitoring and educating the patient about the retinal signs of an impending stroke.
• SD-OCT and OCTA. These devices provide information on retinal vascular perfusion, ischemia and/or swelling, as observed in RAO. Analysis of retinal nerve fiber layer or ganglion cell defects due to these conditions or post-stroke can also be observed. OCTA provides valuable information on ischemic vascular changes through time, including collateral formation, regression or re-perfusion of the ischemia area.

MANAGEMENT PROTOCOL

In light of the aforementioned warning signs, management has changed to lower the risk of stroke.

Given the high risk of stroke in TIA and RAO patients, instead of working them up, they should be sent to the hospital or nearest stroke center for emergent evaluation, extensive work-up and MRI or MRA of the brain.

We need to educate our patients regarding stroke risks and signs, even with the earliest HTR, refer at-risk patients for prompt assessment and management, and work closely with the patient’s health care team.

As we may be the first medical professional a patient encounters, it is imperative we check for warning signs of strokes. Doing so may save lives and prevent disabilities. OM

DR. REYNOLDS is an associate professor at at Nova Southeastern University College of Optometry and clinical preceptor of the college’s diabetes and macular clinic. She was awarded the National Optometric Association Optometrist of the Year in 2013 and is a Fellow in the American Academy of Optometry and the Optometric Retinal Society.