Exposure to sunshine increases the risk of eye cancer, with blue-eyed people more at risk than those with dark eyes, doctors reported Wednesday.

A team led by Dr. Margaret Tucker of the National Cancer Institute said a recent study suggests exposure to ultraviolet radiation from the sun increases the risk of intraocular malignant melanoma -- a tumor that tends to spread to other organs.

Their findings, reported in the New England Journal of Medicine, add to other research showing the incidence of melanoma of the skin rises with exposure to sun. Both types of melanoma develop from the same type of cell, that which produces melanin -- the pigment of the skin, hair and eyes.

Intraocular malignant melanoma is the most common primary intraocular malignant tumor in adults in the U.S. and Europe. It primarily affects older people, almost exclusively whites, and is a serious cause of death and vision loss.

The disease strikes individuals at a rate of 4.9 to 7.5 per million.

Tucker and her colleagues compared 444 patients with intraocular melanoma who were evaluated at Wills Eye Hospital in Philadelphia with noncancer patients who had detached retinas. The patients or their next of kin were interviewed to ascertain their exposure to sun.

Blue-eyed subjects had the highest risk of the eye melanoma and were followed closely by those with green, gray or hazel eyes, the study showed. People with more than 100 freckles, which indicated both exposure and sensitivity to the sun, were significantly more likely to have iris melanoma, Tucker said.

Being born in the southern U.S. was associated with an approximately threefold increased risk of intraocular malignant melanoma.