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Diabetes and Circulation
Patients suffering from either type 1 or type 2 diabetes mellitus are at an increased risk for a wide array of health complications. Chief among these are vascular and coronary diseases.
Diabetes causes widespread changes in normal blood flow due mostly to atherosclerosis, or the development of fatty plaques in major arteries, and hypertension, or high blood pressure. As a result of this abnormal blood flow, diabetic patients often develop secondary complications due to a disease that affects arteries in other parts of the body, peripheral artery disease (PAD). This has the potential to develop into microangiopathy, which is damage to small blood vessels and capillaries caused by chronically high levels of circulating blood glucose (hyperglycemia).
Diminished eyesight or loss of vision is a possible secondary complication. There are a few disorders, caused by microangiopathy, that can cause this problem. One is retinopathy, a disorder of the soft, light-sensitive inner portion of the eye. Another is non-arteritic anterior ischemic optic neuropathy (NA-AION).
Arteritic anterior ischemic optic neuropathy (A-AION) is a result of another condition called giant cell arteritis (also known as temporal or cranial arteritis). Anterior ischemic optic neuropathy in diabetes patients is always non-arteritic, although diabetes is not the sole risk factor associated with NA-AION.
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Causes of NA-AION
Anterior ischemic optic neuropathy in diabetes patients of the non-arteritic type has only one cause, but there are two ways it can occur. However, one form is far more common than the other. The first, less common cause is a blocking by an embolus in the posterior ciliary arteries which surround and feed the optic nerve head, where the nerve attaches to the posterior portion of the eye. This obstruction of blood flow causes swelling in the optic nerve head and leads to diminished visual acuity.
The other more common cause of ischemia in the optic nerve head is diminished blood flow in the ciliary arteries. This causes lower than necessary blood pressures in those arteries; if the pressure in arteries is too low, oxygen will not cross the space between the vessel and the accompanying tissues, in this case, the optic nerve (conditions known as hypoperfusion or nonperfusion). Without sufficient oxygen, irreparable harm can occur to the optic nerve head.
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Patients experiencing NA-AION do not generally perceive any pain as a symptom of the disease. There are few readily observable symptoms and the patient's eyes usually appear normal. The primary symptom is a sudden loss of visual acuity and visual field, most often in only one eye. Patients can sense the difference by placing an open hand over one eye, and then the other. They notice blurred or dim vision. Physicians would notice a swollen optic nerve head upon closer inspection of the eye.
It is worth noting that diabetic patients tend to experience NA-AION during middle age; the disease may progress if the underlying diabetes is not adequately treated. In healthy populations, ischemic optic neuropathy generally occurs in patients in advanced ages.
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Prognosis and Treatment
If treated quickly, the risk of vision complications in the other eye decreases. Unfortunately, there is little that can be done to recover the diminished portion of a patient's vision following NA-AION. Physicians generally recommend immediate high-dosage corticosteroid therapy, which will taper off as vision stabilizes. Other pharmacological approaches include aspirin and drugs to reduce intraocular pressure. Physicians suggest that these treatments may help keep blood flow from being impinged to the optic nerve. Other therapies involve working to reduce risk factors that can result in compromised blood flow such as proper diet, exercise and smoking cessation.
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University of Iowa Department of Ophthalmology and Visual Sciences: Anterior Ischemic Optic Neuropathy, Dr. Sohan Singh Hayreh
International Diabetes Federation Diabetes and Cardiovascular Disease: How Does Diabetes Lead to CVD?
North American Neuro-Ophthalmology Society: Anterior Ischemic Optic Neuropathy
Bulletin of the New York Academy of Medicine: Anterior Ischemic Optic Neuropathy: Diagnosis and Management
The John Hopkins Vasculitis Center: Giant Cell Arteritis Information
American Diabetes Association: Eye Complications
Low Vision: Ischemic Optic Neuropathy