O'lne McCabe, right, ophthalmologic surgeon Emerson Hospital in Concord, with baby William and his mother after she performed cataract surgery on baby William.

CONCORD -- The patient -- snub nose, a shock of black hair, and clad only in Pampers -- looks impossibly vulnerable on the operating table, tubes snaking from his seven-pound body. But without this early surgery to remove a cataract clouding his left eye, William, just 1 month old, would never learn to see.

"The brain ignores images sent from the eye after two months, so the prognosis is worse with the passage of time," said O'Ine McCabe, an ophthalmologic surgeon at Emerson Hospital. "If nothing is done, these cataracts will lead to blindness and irreversible amblyopia (lazy eye)."

Cataract surgery for infants, while rare, isn't new. Emerson has offered the procedure since the early 1980s, about a decade after it was first perfected by ophthalmologic surgeons as a solution to the eye problem that most associate with the elderly.

The stakes cataracts pose for adults, however, aren't nearly as high as they are for small fry. If left untreated, or treated too late, cataracts can lead to permanent problems in parts

of the brain where vision is controlled, and possibly blindness in one or both eyes. Surgeons usually try to address the problem before children are three months old, although those operated on just after this age stand a reasonable chance at developing normal eyesight as well.

Babies are born relying on senses other than sight, particularly smell and sound, but develop vision rapidly during the first six months of life. By about two months, sight replaces sound as the dominant sense. As with other critical developmental periods, if the baby doesn't receive enough stimulation to the vision centers in the brain, those parts may languish, affecting his vision permanently.

McCabe and her colleagues, James Umlas and William Boger III, head Emerson's infant cataract surgery team. McCabe, who has done mission trips to treat infants in El Salvador, also consults at Children's, Winchester Hospital, Mount Auburn, Brigham and Women's, and Beth Israel Deaconness hospitals. McCabe estimates she's done about 150 eye surgeries on babies, most of whom were referred through their pediatricians when the problem was spotted at a well-baby checkup.

Young or old, the condition is the same. Cataracts develop when the lens -- the part of the eye that enables images to focus on the retina -- degrades and becomes opaque, or milky, a problem that's usually linked to advancing age. According to the National Eye Institute, half of Americans over age 80 have cataracts. Of the eight million cataract surgeries performed annually, about 90 percent of adults actually have better vision after surgery.

The cause of childhood cataracts, however -- which can affect one or both eyes and range in severity from slightly milky to fully opaque lenses -- isn't always known. Sometimes, the condition is inherited. In other instances, infections developed in utero or shortly after birth, such as German measles, cause them. Still other children develop them later in childhood, possibly due to exposure to certain drugs like steroids, radiation for cancer treatment, or other problems such as retinal disease. Cataracts are also common in children with Down syndrome, although they're often not serious enough to warrant surgery.

After diagnosis -- which usually involves a series of visual tests -- surgeons slice open the aqueous humor (the white "jelly" of the eyeball) with a tiny scalpel to pry out the clouded lens, which lies just behind the colored iris and, if the child is old enough, replace it with an artificial plastic one. As the eye doesn't finish its growth until age 8, infants' eyeballs are remarkably small, so the incision McCabe makes is just 2.6 millimeters long. There is little bleeding after surgery, and usually a single dissolvable stitch is required.

Most parents are sent home with eye drops to ward off pain and infection. It takes about three weeks to heal, a period during which the babies usually wear a patch over the good eye so that the operated-on eye has a chance to stretch its new muscles and begin what will be a lifetime correspondence with the brain. After that, children younger than 18 months are fitted with contact lenses or, more rarely, glasses.

Dealing with such precious patients, McCabe said, is the best part of the job, though she acknowledges any surgery is difficult news for parents who always expect and want "a perfect child." And because the surgery is considered routine, there is an excellent chance it will go off without a hitch, although she cautions that complications are always possible.

"It can be devastating when you get the news," McCabe said, "but these cataracts are treatable. Very often there are tears involved, but I tell parents taking the cataract out is the easy part; it's what's down the road that's a little bit harder."