The supplement has been found to stave off the devastating condition age-related macular degeneration, or AMD.
Half a million people in Britain suffer from the condition, which leaves victims unable to recognise faces, read or drive.
Striking after the age of 50, it can lead to total blindness, with about 90 per cent of cases proving untreatable.
Scientists who fed vitamin D to middle-aged mice for six weeks noted improvements in their vision. Levels of amyloid beta, a toxic protein linked to Alzheimer’s disease and known to be a hallmark of ageing, were also reduced in the animals’ eyes and blood vessels.
It is believed boosting vitamin D intake may help prevent loss of vision in older people.
Lead scientist Professor Glen Jeffery of University College London said: “Finding that amyloid deposits were reduced in the blood vessels of mice that had been given vitamin D supplements suggests they could be useful in helping to prevent a range of age-related health problems, from deteriorating vision to heart disease.”
Anyone thinking of taking vitamin supplements should consult their doctor
Taking vitamin D supplements in the early stages of AMD “may prove a very simple and effective route to limit disease progression”, the researchers wrote in the journal Neurobiology of Aging.
Clara Eaglen, of the charity for the blind RNIB, said: “Further research is needed, but the initial results are encouraging and we will follow developments with great interest. Anyone thinking of taking vitamin supplements should consult their doctor.”