Optician India

Welcome to question of the day #126

How does vitamin A deficiency affect the eyes?

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. See figure.

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.