Vitamin B12 deficiency: Signs may include progressive bilateral but painless vision loss

Dr Dawn Harper on signs of vitamin B12 and vitamin D deficiency

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Vitamin B12 is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement and a prescription medication. When lacking in this essential vitamin a host of health problems may ensue including those found in your eyes.

Disturbed or blurred vision can also occur as a result of a Vitamin B12 deficiency.

This happens when the deficiency causes damage to the optic nerve that leads to your eyes.

The nervous signal that travels from the eye to the brain is disturbed due to this damage, leading to impaired vision.

Optic neuropathy results in progressive, bilateral, painless vision loss that is often associated with reduced colour vision and central or cecocentral scotomas.

“The optic nerve may appear normal in the early stages of disease until optic atrophy develops,” said Optometric Education.

The health site added: “In approximately 30 percent of cases, the visual deficiencies precede other neurological and haematological signs often due to the presence of folic acid.

“Optic nerve head involvement (in the form of optic atrophy) is rare but can lead to significant visual decline.”

One case study involving a 63-year-old male presented to the eye clinic for a second opinion following a gradual decline in his vision over the previous two months.

An in-depth chart review revealed that the patient had been diagnosed with vitamin B12 deficiency as a result of routine bloodwork.

At that time, he was prescribed vitamin B12 1000 mcg po daily and folic acid 1 mg po daily.

“The patient’s primary care provider consulted haematology, and treatment was amended to intramuscular cyanocobalamin 1000 mcg/mL once weekly for four weeks and monthly thereafter to be followed by folic acid 1 mg daily po,” noted the study.

It added: “This change was recommended because incompletely treated vitamin B12 deficiency with oral replacement by folic acid can aggravate the neurological impairment related to B12 deficiency if the B12 is not corrected first.

“The goal was to ensure vitamin B12 was bioavailable in the presence of any malabsorption issues the patient may have had secondary to the previous gastric ulcer surgery.”

The patient was then later diagnosed with bilateral optic neuropathy due to vitamin B12 deficiency.

“The patient reported his vision was stable and was instructed to continue the cyanocobalamin injections.”

Cyanocobalamin is a man-made form of vitamin B12 used to treat low levels of this vitamin.

It is a is a synthetic form of vitamin B12 that’s not found in nature.

Cyanocobalamin is used more frequently in supplements, as it’s considered more stable and cost effective than other forms of vitamin B12.

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