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Nutritional and Toxic Optic Neuropathies

(Toxic Optic Amblyopia; Nutritional Optic Amblyopia)

By

James Garrity

, MD, Mayo Clinic College of Medicine

Last full review/revision Oct 2021| Content last modified Nov 2021
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Topic Resources

Nutritional and toxic optic neuropathies are damage to the optic nerve caused by undernutrition (nutritional optic neuropathies) or by exposure to a substance that is harmful to the optic nerve, such as lead, methanol (wood alcohol or methyl alcohol), ethylene glycol (antifreeze), or certain drugs (toxic optic neuropathies).

  • A nutritional deficiency or toxic substance is often the cause of optic neuropathy.

  • Vision usually deteriorates gradually.

  • People should avoid further exposure to toxic substances or take nutritional supplements.

Causes

An optic neuropathy that is caused by a nutritional deficiency (especially of vitamins B1 and B12 or folate [folic acid; see also Overview of Vitamins Overview of Vitamins Vitamins are a vital part of a healthy diet. The recommended dietary allowance (RDA)—the amount most healthy people need each day to remain healthy—has been determined for most vitamins. A safe... read more ]), is called nutritional optic neuropathy. Alcoholics and people who have had bariatric (weight-loss) surgery are particularly susceptible to nutritional optic neuropathies. The actual cause is probably undernutrition rather than a toxic effect of alcohol.

Rarely, toxic optic neuropathy is caused by drugs (such as chloramphenicol, isoniazid, ethambutol, and digoxin) or toxins such as lead, ethylene glycol (antifreeze), or methanol (wood alcohol or methyl alcohol).

Symptoms

In people with nutritional or toxic optic neuropathies, vision deteriorates gradually over days to weeks. A blind spot may develop and gradually enlarge. It may not be noticed at first. Color vision may be affected more severely than the loss of visual acuity (visual resolution). Both eyes are usually affected.

Ethylene glycol and particularly methanol poisoning can cause sudden, complete loss of vision. Both substances can cause other serious symptoms such as coma, difficulty breathing, vomiting, and abdominal pain.

Did You Know...

  • Drinking antifreeze (ethylene glycol) or methanol (wood alcohol or methyl alcohol) can cause sudden and complete vision loss.

Diagnosis

  • A doctor's evaluation and sometimes testing

Doctors base the diagnosis of nutritional or toxic neuropathies on the person's history of undernutrition or exposure to toxic or chemical substances, their eye symptoms, and the results of a vision test. Sometimes testing for toxins or for a vitamin deficiency is done.

Prognosis

With prompt treatment, most people with nutritional and toxic optic neuropathies recover some of their lost vision.

Treatment

  • For undernutrition or alcohol use, vitamin supplements and avoidance of alcohol

  • Treatment of drug or toxin causes (such as chelating drugs for lead or hemodialysis and fomepizole for ethylene glycol or methanol)

If alcohol use or undernutrition is a cause of a nutritional optic neuropathy, the person should stop drinking alcohol, eat a well-balanced diet, and take vitamin supplements that include folate and B vitamins. However, if the cause is mainly vitamin B12 deficiency, treatment with dietary supplements alone is not enough. Vitamin B12 deficiency is typically treated with injections of vitamin B12.

People with toxic optic neuropathies should avoid alcohol and other chemicals or drugs that may be toxic. If lead is the cause of toxic optic neuropathy, chelating drugs Treatment Some causes of lead poisoning are ingesting lead paint and eating or drinking from certain imported, improperly lead-glazed ceramics. Very high levels of lead in the blood may cause personality... read more (such as succimer or dimercaprol) help remove it from the body. If ethylene glycol or methanol poisoning is the cause, rapid treatment with hemodialysis Hemodialysis Dialysis is an artificial process for removing waste products and excess fluids from the body, a process that is needed when the kidneys are not functioning properly. There are a number of reasons... read more Hemodialysis to remove these toxins and the antidote drug fomepizole may help. Ethyl alcohol (ethanol), a paradoxical alternative, may also help by competitively inhibiting the metabolism of the toxin (ethylene glycol or methanol) to a harmful metabolite (byproduct).

Magnifiers, large-print devices, and talking watches (low-vision aids) may help people with loss of vision.

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