A man in Pennsylvania says he contracted an eye-eating parasite from an amusement park water ride, and he is suing the park for negligence.

Robert Trostle claims that he contracted the parasite microsporidia in his left eye from being splashed during a ride at Pittsburgh's Kennywood amusement park in early July.

In a complaint filed in Allegheny County civil court on Tuesday, Trostle said his eye became itchy, red, painful, and sensitive to light in the days following a July 2 ride on Kennywood's Raging Rapids, which simulates white-water rafting.

He was given antibiotics after being diagnosed with acute conjunctivitis – pinkeye – but his symptoms continued to get worse, his lawsuit claims. He underwent "an extremely painful surgery where the parasite was scraped out of the eye with a surgical scalpel," after being diagnosed with microsporidia keratitis on July 14, according to the complaint.

The parasite was "unable to be removed" during surgery, the complaint says, and Trostle continues to suffer from blurry vision, redness, itchiness, dryness, inflammation and pain.

A Kennywood spokesman said the park does not comment on active litigation.

"Safety is the top priority of Kennywood in everything we do, and that certainly extends to maintenance of the rides and water used in rides," the spokesman, Nick Paradise, said in an emailed statement.

The lawsuit claims that the Raging Rapids ride's water was "dirty, stagnant and sludge-like," and said that the park failed to adequately regulate, inspect, and filter the water.

Trostle is seeking at least $35,000 of damages in the lawsuit.

According to the Centers for Disease Control and Prevention, parasitic keratitis is a "rare but serious infection of the eye that can cause permanent vision loss or blindness," after infecting the cornea, the transparent part of the eye that covers iris and pupil.

Some 85 percent of infections come from people wearing contacts, according to the CDC.

It can be difficult to treat, according to the CDC, typically requiring "aggressive medical and surgical treatment."

The parasite that causes it is common in nature and can be found in tap water, heating, ventilating and air-conditioning units, and hot tubs, according to the CDC.

Still its incidence is relatively low: Studies have estimated its prevalence at 1.2 cases per million adults and as many as two per 10,000 soft contact lens wearers per year.

The number of cases rose dramatically in the 1980s as more people began to use soft contact lenses, non-sterile contact lens solutions and homemade saline tablets, according to studies cited in a 2013 report. Outbreaks have been linked to contaminated water supplies and floods, the report said.