Oral Vitamin A deficiency Adult: For severe deficiency with corneal changes: 500,000 units daily for 3 days, followed by 50,000 units daily for 2 wk and then 10,000-20,000 units daily for 2 mth as follow-up therapy. For cases with corneal changes: 10,000-25,000 units daily until clinical improvement occurs (usually 1-2 wk).