Teen suffers vision loss after parasite found living in his eye

For one unfortunate Mexican teenager, an unwanted tenant living in his eye led to what may be a permanent loss of vision, doctors report.

As published Sept. 21 in The New England Journal of Medicine, an unnamed 17-year-old boy from a rural town in Mexico came to a hospital after suffering impaired vision and pain in his right eye for three weeks.

According to ophthalmologists Drs. Pablo Guzman-Salas and Juan Serna-Ojeda, an examination showed an inflamed cornea, blood in the back of the eye, "multiple iris perforations" and other eye damage.

The cause?

"A flattened and mobile trematode [tiny flatworm] was seen moving freely" at the back of the eye, according to the doctors. The parasite was traveling -- through holes it had made in the eye's iris -- between the front and back portions of the eye.

The doctors said the boy was given praziquantel, a drug used to treat parasitic infections, and then underwent surgery to physically remove the worm, upon which even more damage to the eye was noted.

The worm "was removed in multiple pieces and [its species] could not be more specifically identified," said the physicians, who work at the Institute of Ophthalmology Conde de Valenciana in Mexico City.

Unfortunately, they said, six months later there was no improvement in vision in the boy's right eye.

How did he become host to the tiny worm? According to the physicians, the boy reported that he had not ingested foods that might contain the worm, nor had he swum in lakes where he might have contacted the creature.

Stool samples also showed no evidence of parasitic infection, they added.

Two U.S. eye doctors said such cases, while very uncommon, can happen.

"This is a rare, but well-known -- to ophthalmologists at least -- cause of vision loss," said Dr. Jules Winokur, an ophthalmologist at Lenox Hill Hospital in New York City.

"Animals such as dogs, raccoons, skunks, fish or frogs can carry the parasite, and people can get infected either through ingesting the eggs or through contact with invasion through the skin," he said.

And infections with these tiny parasitic worms can occur in the United States, Winokur added.

"While rare, certain areas are known to harbor these parasites, including parts of the Midwest and Southeast of the United States," he said.

Dr. Matthew Gorski is an ophthalmologist at Northwell Health in Great Neck, N.Y. He agreed that parasitic worms can affect the eye and cause major damage.

"Symptoms can range from mild to severe vision loss, blind spots, floaters and pain," Gorski said. "Treatment consists of a combination of laser surgery, oral medication, eye drops and eye surgery. Though rare, the effects of a nematode in the eye can be devastating to one's vision and quality of life."