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A drug which is already licensed for use could be used to treat sight problems in some albino people, say US researchers.

People with albinism produce little or no melanin, which has a range of health consequences including poor sight and greater risk of skin cancer.

, doctors said a drug increased melanin production in mice.

Other doctors described the work as a "substantial leap forward".

People with a type of albinism - OCA1 - have light skin, white hair and light irises caused by defective tyrosinase genes which mean they struggle to produce melanin.

Scientists at the National Eye Institute, Maryland, were investigating a drug - nitisinone - which is used to treat a blood condition, but is also known to increase hair and eye pigmentation.

Giving the drug to albino mice increased the amount of melanin in the eyes after one month of treatment.

However, the researchers could not tell it this improved eyesight in the mice as the generally nocturnal creatures have different eye structures.

The researchers also do not know what would happen in human patients.

"A significant unanswered question is whether improving pigmentation in patients with albinism would improve visual function," the report said.

However, they added it was: "plausible that increasing pigmentation may help with symptoms".

Dr Prashiela Manga and Dr Seth Orlow, from New York University School of Medicine, said the study "represents a substantial leap forward toward the possible treatment of all forms of oculocutaneous albinism (OCA)".