Causes and risk factors
Toxic optic neuropathy occurs as a result of continued intake of toxic substances such as alcohol, tobacco, and certain drugs. The drugs that cause TON include certain antibiotics, anti-tuberculosis medication, and chloramphenicol, amongst others. Occupational exposure to substances such as methanol, ethambutinol, and amiodarone has also been identified as causative factors for toxic optic neuropathy.
Clinical presentation
Toxic optic neuropathy gives rise to gradual bilateral loss of vision. The color vision becomes abnormal, known as dyschromatopsia. There is loss of visual acuity. The vision progressively deteriorates. Some patients may develop total blindness.
Investigations
A detailed ophthalmic examination will be carried out. The optic disc may appear swollen and hyperemic. Hemorrhages may be observed around the disc. The pupillary response to light may be normal, weak, or absent.
Blood tests are performed to measure levels of the toxic substances. Imaging tests such as CT or MRI may be recommended.
Treatment
The treatment of toxic optic neuropathy consists of identifying and eliminating the toxic substance from the body.
Complications
Toxic optic neuropathy can extensively damage the optic nerve, causing optic atrophy.
When to contact a doctor
Contact a doctor as soon as you experience any degree of vision loss.
Prevention
Toxic optic neuropathy can be prevented by refraining from chewing tobacco and drinking alcohol.
Facts and figures
All races, all ages, and both genders are equally affected by toxic optic neuropathy.
Systems involved
Ophthalmic, CNS
Organs involved
Eyes, nerves
