A is for vitamin A

Writings from the school of Hippocrates recommended that patients afflicted with night blindness be treated with ‘raw beef liver, as large as possible … to be taken once or twice by mouth’.5 Vitamin A (abundant in liver, but present only as the precursor β-carotene in carrots) is essential for a healthy cornea. Deficiency leads to xerophthalmia and eventually corneal destruction. Night blindness is an earlier manifestation caused by decreased synthesis of the photopigment rhodopsin in the retina. Restriction of visual fields, photophobia and reduced visual acuity follow.

Malnourished patients from the developing world, and those who malabsorb fat (and so fat-soluble vitamins A, D, E and K), are predominantly affected. Clues to the diagnosis include Bitot's spots (whitish patches of keratin debris in the conjunctiva, figure 1), corneal abnormalities and, late in the disease, hypopigmentation in the peripheral retina. Electroretinography shows increased thresholds of photoreceptors (rods>cones), and absent potentials in severe cases.6 Although treatment has progressed in the past 2000 years, vitamin tablets and fish oil a diet rich in liver is still used where these are unavailable.