CHAPEL HILL, N.C. — Some premature babies are born with the odds stacked against them. Many develop an eye condition called retinopathy, the leading cause of vision loss in children.

The decision to treat preemies for the problem has been tricky, because the babies are so small. Now, early treatment may be the key to saving sight.

With 3-year-old twins, Amy May barely has time to think, but says she enjoys every minute of the chaos. At times, she says it is hard for her to remember how small her twins once were.

"They almost didn't look like babies they were so tiny," May said.

Ryan and Grace were born 13 weeks early. Ryan weighed 2 pounds 3 ounces. Grace barely weighed a pound.

From the day they were born, the twins had life-threatening problems.

"Keeping them breathing, keeping them eating, growing," May said.

Then the twins developed retinopathy of prematurity, or ROP, a common eye problem for preemies.

With ROP, blood vessels in the eye develop abnormally, causing scarring and even blindness if the retina detaches.

Doctors start screening preemies for ROP when they are 1 month old. They used to wait until the infant was at a high risk for vision loss before performing corrective surgery.

According to a new study, treating ROP earlier -- on average, two weeks -- cuts the risk of vision loss by more than one-third.

"Two weeks can make a big difference between treating an eye at the right time and treating a little too late," said Dr. David Wallace, an ophthalmologist at the University of North Carolina Hospitals.

The results offer peace of mind to ophthalmologists.

"We were relieved, because we feel like we're doing the right thing now," Wallace said. "Before, we'd treat earlier in some cases, but we weren't sure."

Early intervention paid off for Ryan and Grace. They were in the study and had laser eye surgery.

"Both of them wear glasses and they probably will for the rest of their life, but their vision is almost 20/20 corrected," May said.

The twins still travel to UNC for regular eye exams. So far, they are doing much better than their doctors and parents expected.

"We have really, really been blessed," May said.

The babies, who were no bigger than the palm of a hand, are now real handfuls.

Babies who weigh less than 3.5 pounds at birth are at high risk for retinopathy. Not all cases are severe enough to cause vision loss.

Surgery carries some risks, including peripheral vision loss and cataracts.