What is the recommended dose of vitamin A (International Units) for treating evening blindness due to vitamin A deficiency?

Treatment of Vitamin A Deficiency with Evening Blindness

For adults with vitamin A deficiency manifesting as evening blindness, administer 10,000 to 25,000 IU oral vitamin A daily for 1-2 weeks to achieve clinical improvement. 1

Diagnosis and Assessment

When a patient presents with evening blindness (nyctalopia), vitamin A deficiency should be strongly suspected. This is often the earliest clinical manifestation of vitamin A deficiency, which can progress to more severe ocular manifestations if left untreated.

Key diagnostic considerations:

• Confirm vitamin A deficiency through serum retinol levels
• Assess for other symptoms of vitamin A deficiency:
  • Xerophthalmia (dry eyes)
  • Conjunctival xerosis (with or without Bitot spots)
  • Corneal xerosis (which can progress to ulceration)

Treatment Protocol for Adults

Initial Treatment Phase

• Dosage: 10,000 to 25,000 IU oral vitamin A daily for 1-2 weeks 1
• Higher doses may be needed if the patient is experiencing night blindness 1
• Use water-miscible forms of vitamin A if available, as they may improve absorption, especially in patients with malabsorptive conditions 1

Monitoring and Follow-up

• Recheck vitamin A levels at 3 months after initiating treatment 1
• If symptoms persist or vitamin A levels remain low despite oral supplementation, refer to a specialist for consideration of intramuscular vitamin A injections 1

Special Considerations

• For patients with severe deficiency or those who don't respond to oral therapy, consider referral for specialist assessment 1
• For pregnant women, limit vitamin A intake to below 10,000 IU/day due to potential teratogenic effects 2

Treatment Protocol for Special Populations

Children (6 months to 5 years)

• Children with vitamin A deficiency should receive 200,000 IU on day 1,200,000 IU on day 2, and 200,000 IU 1-4 weeks later 1
• Children less than 12 months of age should receive half doses (100,000 IU) 1

Pregnant Women

• Assess vitamin A intake and blood levels before conception or early in pregnancy 1
• Keep vitamin A supplementation below 10,000 IU/day to avoid potential harm to the fetus 2
• Consider using beta-carotene form of vitamin A instead of retinol for pregnant women 1

Maintenance Therapy

After achieving clinical improvement:

• Continue monitoring vitamin A levels annually 1
• Adjust supplementation as needed to maintain normal serum levels
• Ensure adequate dietary intake of vitamin A-rich foods

Clinical Response Timeline

Improvement in night vision typically occurs rapidly:

• Initial improvement in rod function may be seen within the first week of treatment 3
• Near-normal recovery of visual function can be expected after approximately 1 month of supplementation 3
• Full recovery of dark adaptation may take up to 5 months in some cases 4

Cautions and Contraindications

• Avoid excessive supplementation to prevent vitamin A toxicity
• Acute toxicity can occur with ingestion of >300,000 IU in adults 2
• Chronic toxicity can result from prolonged ingestion of >25,000 IU daily for >6 years 2
• Monitor for signs of toxicity: headaches, nausea, skin disorders, increased intracranial pressure

By following this treatment protocol, most patients with vitamin A deficiency-related evening blindness should experience significant improvement in symptoms and prevention of more severe ocular complications.