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Toxic and Nutritional Amblyopia

(Nutritional Optic Neuropathy)

By

James Garrity

, MD, Mayo Clinic College of Medicine

Last full review/revision Jun 2020| Content last modified Jun 2020
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NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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Topic Resources

Toxic amblyopia is damage to the optic nerve caused by undernutrition 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.

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

  • Vision usually deteriorates gradually.

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

Because the symptoms of toxic amblyopia can differ from the amblyopia that occurs most often in young children, it is sometimes called an optic neuropathy (toxic optic neuropathy or nutritional optic neuropathy) instead of amblyopia.

Causes

Toxic amblyopia may be caused by a nutritional deficiency (sometimes called nutritional amblyopia), especially of vitamins B1 and B12 or folate (folic acid; see also Overview of Vitamins). Alcoholics and people who have had bariatric (weight-loss) surgery are particularly susceptible to nutritional amblyopia. The actual cause is probably undernutrition rather than a toxic effect of alcohol.

Rarely, toxic amblyopia 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 toxic amblyopia, vision deteriorates gradually over days to weeks. A blind spot may develop and gradually enlarge. It may not be noticed at first. If the disorder is caused by exposure to a toxin or to a nutritional deficiency, 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 toxic amblyopia 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 toxic amblyopia 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)

People with toxic amblyopia should avoid alcohol and other chemicals or drugs that may be toxic. If alcohol use or undernutrition is a cause, 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.

If lead is the cause, chelating drugs (such as succimer or dimercaprol) help remove it from the body.

If ethylene glycol or methanol poisoning is the cause, rapid treatment with hemodialysis and the drug fomepizole or, as an alternative, alcohol may help.

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

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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