When Stroke Strikes The Eyes
Circulation issues major concern for people with diabetes
Forgive the silly play on words in my title, but May is National Stroke Awareness Month, and I'd like to spend some time discussing the problem of stroke in people with diabetes from an eye doctor's perspective. Stroke refers to acute loss of blood supply (circulation) to any portion of the brain, resulting in irreversible brain damage and loss of bodily functions controlled by that portion.
The eye is connected to the brain by the optic nerve which, essentially, is a direct extension of the brain (from an anatomist's point of view, much as the spinal cord is also an extension of the brain). Moreover, movement of the eyes is precisely controlled by six pairs of muscles that are directly supplied by three nerves that emerge from the base of the brain (for those who like the details, these are Cranial Nerves III, IV and VI). Because of this direct eye/brain connection, stroke frequently affects both vision and the ability to coordinate the movements of both eyes. In fact, eye doctors commonly examine patients with vision symptoms caused by stroke - or impending stroke (also known as a transient ischemic attack, or TIA).
If blood supply is disrupted only temporarily, patients may notice temporary muscle weakness (typically on one side of the body), difficulty walking, loss of mental function and/or the ability to speak, and dimming of vision (like a window blind being drawn closed for a few seconds). These are classic symptoms of a TIA, and should alert you and your doctor to the strong possibility of an imminent stroke. If loss of circulation is longer lasting, these symptoms will be more pronounced and may last indefinitely – a stroke has occurred. Patients may lose a portion of their vision, depending upon the anatomical location of the blockage; if the back portion of the brain is affected (the occipital cortex), total loss of vision is possible (see visual field defect example below).
Visual Field Defect
Example of partial vision loss as a result of stroke to the left side of the brain.
If the optic nerve itself is affected by stroke, vision is severely affected. This is called ischemic optic neuropathy, and more commonly happens in patients with diabetes, high blood pressure, and other conditions affecting circulation. If the cranial nerves responsible for controlling eye movements lose their blood supply (a condition called ischemic cranial neuropathy), the two eyes will not work together properly and patients often experience double vision, though I have examined numerous patients who are asymptomatic without meticulous examination. Diabetes is notorious for causing this condition, which, fortunately, usually resolves on its own within three to six months time. These patients are, however, at increased risk for a more serious stroke event at a later date.
Stroke is the third leading cause of death in the U.S. and the leading cause of severe disability. People with diabetes are two and one half times more likely to suffer a stroke than people without diabetes. In fact, a recent study suggests that even younger patients recently diagnosed with type 2 diabetes (< 5 years) have twice the risk of stroke compared to the general population. The key to reducing these tragic statistics is public education about prevention, recognition of symptoms, and the importance of immediate medical care. For those of us with diabetes, we can drastically lower our risk a few ways:
- by keeping our blood glucose and blood pressure as well-controlled as possible
- by getting regular physical activity and appropriate nutrition
- by not smoking
- by talking about stroke and working with our doctors to uncover and reduce our risk factors
- by learning all we can about prevention.
Stroke is definitely one condition where prevention is the best treatment strategy.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
Read more about Dr. Chous here.
Visit Dr. Chous' website here.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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