48- Ischaemic optic neuropathy. Optic atrophy- primary and secondary:
Anterior Ischaemic optic neuropathy is a medical condition involving loss of vision caused by damage to the optic nerve as a result of insufficient blood supply. This form of ischemic optic neuropathy is generally categorized as two types: arteritic (AAION) in which the loss of vision is the result of an inflammatory disease of arteries in the head called temporal arteritis, and nonarteritic (NAION) which is due to non-inflammatory disease of small blood vessels.
Causes:
Non-arteritic anterior ischaemic optic neuropathy:
The exact reason for the reduced blood flow in NAION is unknown. NAION is the most common type of ischemic optic neuropathy and usually occurs in individuals over 40. Most people who develop NION have underlying high blood pressure, diabetes, sleep apnea or high cholesterol. Smoking may increase the risk of developing NAION. Rarely some medications have been known to cause NAION.
Arteritic anterior Ischaemic optic neuropathy:
A less common type of ION occurring in people over 50 years of age. This disease is an inflammatory disease that affects certain medium to large-sized blood vessels, including those in the eye. The exact cause of the inflammation is unknown, but the inflammation of the blood vessels cause a loss of blood flow to the optic nerve
Clinical features:
Sudden loss of central or side vision is the most common symptom. There may be loss of side vision in the lower half of reading vision. ION generally does not cause any other symptoms, such as pain or double vision. People with temporal arteritis often have many more symptoms. Headaches, and tenderness over the temple region is common. Joint aches and pains commonly affect the shoulders and hips. They may also feel tired and run a fever, combined with recent weight loss.
Diagnosis:
- Complete eye examination, including pupil dilation. Decreased blood flow usually results in swelling of the optic nerve
- A test of side vision (visual field) may also be performed. In addition, a blood test and/or biopsy of an artery in the temple to diagnose temporal arteritis may be required.
Treatment:
NAION: there is no proven treatment. Involvement of the other eye occurs in about 20-30% of people. Any underlying diabetes, high blood pressure, high cholesterol or sleep apnea should be kept under control.