The ability to see in poor light depends on the presence of a substance in the eye called rhodopsin, or visual purple. It is destroyed by bright light but rapidly regenerates in the dark. However, for some people, the adaptation to darkness or the recovery from glare takes an unusually long time. There is no medical treatment for this condition.

The herb bilberry, a close relative of the American blueberry, is the most commonly mentioned natural treatment for impaired night vision. This use dates back to World War II, when pilots in Britain's Royal Air Force reported that a good dose of bilberry jam just before a mission improved their night vision, often dramatically. After the war, medical researchers investigated the constituents of bilberry and found a group of active chemicals called anthocyanosides. These naturally occurring antioxidantsappear to have numerous potentially important actions within the eye.10,11

However, neither anecdote nor basic scientific evidence of this type can prove a treatment effective. Only double-blind, placebo-controlled studies can do that. (To learn why this is so, see Why Does This Database Rely on Double-blind Studies?) The current evidence from studies of this type is more negative than positive, with all of the most recent studies finding no benefit.

For example, a double-blind crossover trial of 15 individuals found no short- or long-term improvements in night vision attributable to bilberry.1 Similarly negative results were seen in a double-blind placebo-controlled crossover trial of 18 subjects 2and another of 16 subjects.3Earlier studies had reported some benefit, but they were less rigorous in design.4-9

Thus, at present, bilberry cannot be recommended as a treatment for improving night vision. For more information, including dosage and safety issues, see the full bilberry article.