Eye stroke: optic nerve infarct (NAION)

NAION is a medical condition characterized by sudden damage to the optic nerve due to an interruption in blood supply to the small blood vessels nourishing the optic nerve head. This disruption leads to swelling and edema of the optic nerve head, sometimes accompanied by small hemorrhages. The result is a sudden, usually painless, loss of vision that can affect the entire visual field or only a portion of it.

The exact cause of NAION is not always clear, but numerous risk factors are associated with vascular diseases. These include diabetes, high blood pressure, high blood lipid levels, smoking, and kidney disease. Other conditions such as sleep apnea, anemia, and a crowded optic nerve head (referred to as a disc at risk) can also increase susceptibility. In addition, the use of certain medications, particularly drugs for erectile dysfunction or pulmonary hypertension known as PDE5 inhibitors, has been linked to the development of NAION. Patients who have experienced NAION should consult their doctor before using these medications.

The primary symptom of NAION is a sudden, painless decrease in vision or loss of a portion of the visual field. Patients sometimes first notice the vision loss on waking. The exact trigger is not fully understood; a role for changes in blood pressure during sleep has been proposed but remains debated. The vision loss can range from mild to severe and may affect central vision, peripheral vision, or only the upper or lower half of the visual field.

Diagnosis of NAION is made by an ophthalmologist through a comprehensive eye examination, including evaluation of the optic nerve. The doctor will assess visual acuity, color vision, and perform a visual field test to determine the extent of the damage. It is crucial to rule out other conditions that can cause similar symptoms, particularly arteritic ischemic optic neuropathy (AION), which is associated with giant cell arteritis and requires urgent treatment to prevent blindness in the other eye.

Following a diagnosis of NAION, a thorough evaluation of underlying risk factors will be recommended. This evaluation may include blood tests for glucose and lipid levels, blood pressure monitoring, and assessment for sleep apnea. The goal of this workup is to identify and manage contributing factors, thereby reducing the risk of other cardiovascular events such as stroke or heart attack. In some cases, a doctor may consider recommending medication, such as aspirin, as part of general cardiovascular risk factor management, but not as a specific treatment for NAION or to prevent recurrence in the other eye.

Currently, there is no proven treatment that can restore vision lost due to NAION. Treatment focuses on managing and controlling underlying risk factors. This includes smoking cessation, managing diabetes and high blood pressure, and treating sleep apnea. In some cases, a doctor may consider recommending medication, but medications should never be changed or stopped independently without medical advice. Vision may worsen during the first weeks while the nerve is swollen. Some people later regain part of their central visual acuity without a specific treatment, but field defects often persist. Optic nerve swelling resolves over time and usually leaves permanent nerve damage. Any worsening requires reassessment.

Regular follow up with an ophthalmologist is important to monitor visual status and ensure there is no worsening. It is crucial to report any new changes in vision, new or severe headache, jaw pain with chewing, or scalp tenderness to your doctor immediately. These symptoms, especially in older individuals, could indicate arteritic ischemic optic neuropathy (AION), a more serious condition requiring urgent evaluation and treatment to prevent blindness in the other eye. Do not alter medications or discontinue existing treatments without consulting a physician.