RECOGNISE THE EYE SIGNS, THEN TREAT - THE CORNEAL STAGE BLINDS
Vitamin A Deficiency - StatPearls (NCBI Bookshelf NBK567744) - https://www.ncbi.nlm.nih.gov/books/NBK567744/
The early signs are reversible and the late ones are not, which is the whole argument for treating on the clinical picture rather than waiting for a blood level. The dose row below carries the WHO regimen; what follows here is what to look for and who to treat.
- THE EYE SIGN IS THE DIAGNOSIS - xerophthalmia points to vitamin A deficiency and to almost nothing else. The blood test is for the case that is not clear: order a serum retinol where the history and examination leave doubt, and read anything under 20 micrograms/dL as deficient.
- A NORMAL BLOOD LEVEL DOES NOT CLEAR IT - the serum retinol can read normal while the body's stores are already low, because the liver keeps the circulating level up. Do not use a normal retinol to overrule Bitot spots.
- WHICH EYE SIGNS COME BACK AND WHICH DO NOT - the early ones - night blindness, a dry conjunctiva, Bitot spots - clear entirely on supplementation, generally inside 2 months. Once the cornea dries and ulcerates it scars, and the sight can be lost for good even with treatment. Everything before the cornea is reversible; that is the window.
- THE MORTALITY, WHICH IS THE REAL REASON TO TREAT - a child with night blindness dies at three times the rate of a child whose deficiency is subclinical. With Bitot spots and night blindness together the rate is nine times that. And of children with keratomalacia, close to two-thirds are dead within months. These children do not mostly die of their eyes: once the eye signs appear, the child has become far easier to infect.
- WHAT ELSE CAUSES NIGHT BLINDNESS AND WHITE CONJUNCTIVAL PATCHES - losing night vision is the first thing retinitis pigmentosa does, and some rare retinal dystrophies do the same. Cataract and myopia are degenerative eye diseases that can present that way too. As for the spots: niacin deficiency also goes with Bitot spots, and a pinguecula or a pterygium can be mistaken for one.
- TREAT THE ZINC AT THE SAME TIME - a child who is short of zinc responds poorly to vitamin A, and should have zinc given alongside it. A child who does not respond to vitamin A may be zinc-deficient rather than mis-diagnosed.
- IF THE GUT IS THE PROBLEM, THE MOUTH IS THE WRONG ROUTE - where the deficiency comes of malabsorption, think about giving the vitamin A intramuscularly instead. Coeliac disease, cystic fibrosis and chronic giardiasis all belong in the history.
- WHO DOES NOT NEED IT - above 30 micrograms/dL there is nothing to be gained from supplementing, and the recommended dietary allowance is what such a patient should follow. For a well-nourished child, a varied diet rich in nutrients keeps vitamin A deficiency away, so long as the child is generally well and absorbing food.
- THE LONG-TERM ANSWER IS FOOD, NOT CAPSULES - more programmes are turning to what causes the deficiency in the first place, fortifying food and teaching families, rather than handing out supplements alone.