Vitamin A deficiency affects the conjunctiva, cornea and retina. Here I will concentrate on the anterior eye problems.
Vitamin A deficiency occurs in developing countries and I have seen the ocular effects during my work in Asia and Africa. The damage to the ocular surface is called xerophthalmia-xeros = dry, ophthalmos = eye in Ancient Greek. There are other causes of xerophthalmia other than vitamin A deficiency.
The conjunctiva becomes dry, thick and wrinkled. If untreated, it can lead to corneal ulceration and ultimately to blindness.
World Health Organization classified xerophthalmia into following stages:
- XN-Night blindness
- X1A-Conjunctival xerosis
- X1B-Bitot spots
- X2-Corneal xerosis
- X3A-Corneal ulceration/keratomalacia, involving less than one-third of the cornea
- X3B-Corneal ulceration/keratomalacia, involving more than one-third of the cornea
- XS-Corneal scar due to xerophthalmia
- XF-Xerophthalmic fundus
Each year approximately 8 to 10 million children worldwide, 3 to 5 years in age, develop milder xerophthalmia manifested by night blindness or conjunctival xerosis associated with malnutrition.
Bitot’s spots are the buildup of keratin-fibrous structural protein-located superficially in the conjunctiva. They can be oval, triangular or irregular in shape.
Animal liver and dairy products are very rich sources of vitamin A but this is of no use for those people who choose not to eat meat and other animal products.
The human body can produce vitamin A from carotenoids found in plants such as beta-carotene and alpha-carotene. These are collectively known as provitamin A. However, about 45% of people carry a genetic mutation that significantly reduces their ability to convert provitamin A into vitamin A. Vegetable sources of provitamin A are sweet potato, winter squash, kale and carrots. But people with the genetic mutation may still have vitamin A deficiency even if they consume these vegetables. Vitamin A supplements are useful for these people.