Can a lack of Vitamin A in your diet be statistically proven to be linked to worse eyesight?

Question

Reading this question: Does eating carrots improve your eyesight? - brought to mind a common piece of medical advice in USSR - to eat carrots to prevent your eyesight from going bad (as opposed to that question's claim to improve eyesight).

Is it true that a lack of Vitamin A in your diet can be statistically proven to be linked to worse eyesight?

Any definition of "worse" is acceptable for the purposes of this question, from abnormal eye pressure to nearsightedness to glaucoma to whatever else, though I personally am more interested in near-sightedness.

I don't have a cite for the claim but it was stated repeatedly by different doctors in USSR in my presence.

It sounds at least somewhat plausible in a sense of certain diseases being obviously caused by vitamin deficiencies.

Answer 1

Deficiency of vitamin A most certainly can lead to worsening of eyesight and blindness.

A case study here shows that correction of vitamin A deficiency resulted in reversal of night blindness. It's findings suggest that of all the eye structures effected by vitamin A deficiency, rods and S cones are more likely to be damaged than are L and M cones. Another case can be read here.

A study here is not exactly on-topic but shows data which indicates that vitamin A supplements can prevent blindness in children infected with measles (which is a fairly rare consequence, but still noteworthy).

Loss of visual acuity or blindness due to deficiency of vitamin A from starvation or malnourishment is still a problem faced by many developing countries.

It is also the leading cause of preventable childhood blindness worldwide.

While it is true that a severe deficiency of vitamin A can dramatically worsen eyesight, there is no convincing evidence that an otherwise healthy person can increase his/her vision by consuming more vitamin A.

In fact, consumption of too much vitamin A results in hypervitaminosis A which can be fatal. For reference, one can check the case of Xavier Mertz, the Antarctic explorer who died of this condition.