LUBBOCK, Texas -- Contact lenses which fight infection are likely one day to relieve wearers of the constant bother of taking them out and cleaning them.

The new lenses, coated with a special film that kills the bacteria which cause eye infections, could be worn safely for months at a time.

Scientists in the United States have tested the lenses on rabbits which showed no ill-effects after wearing them for two consecutive months. The lenses are covered with a thin coating of selenium, a natural element found in the soil, plants and foods.

Trials on humans are expected to start soon, and the researchers say they may be on the market in just two years. Dr. Ted Reid, from Texas Tech University Health Sciences Center in Lubbock, Texas, said selenium formed a natural defense against infection. "It's a natural mechanism we use in our body to kill bacteria," he said. "That's why we've had these contact lenses on rabbit eyes for two months and seen no effect whatsoever. I'm ready to put them in my eyes right now."

Several brands of extended-wear contact lenses made from silicone hydrogel are available in the United States and Britain which can be worn for up to 30 days at a time. But most lenses have to be removed and cleaned at least once a week.

The selenium-coated lenses could be worn for at least two months at a time, and possibly longer. Reid told a meeting of the American Chemical Society in Boston, Massachusetts, that the selenium film was only one molecule thick and did not interfere with the performance of the lenses.

The research group is also investigating other applications for selenium coatings, including prevention of secondary cataracts and HIV treatment. Although the work is in the preliminary stage, there was evidence that selenium attached to antibodies can inactivate the AIDS virus in the laboratory, DPA quoted Reid as saying.