A woman had her left eye removed after she caught a difficult-to-treat parasitic infection from showering while wearing her contact lens.

Acanthamoeba keratitis is a rare but serious infection caused by a microorganism that infects the outer covering of the eye, called the cornea. It's most common in contact lens wearers, but anyone can get it, according to the CDC.

Mary Mason, 54, from the UK, was wearing contact lenses for 30 days and believed the organism entered her eye after taking a shower without removing them.

"It would have come under the lens and then multiplied, so my eye was teased with it," she told BBC News.

According to the CDC, bathing while wearing contact lenses or cleaning lenses with tap water puts people at increased risk of developing Acanthamoeba keratitis. It can cause severe pain and blindness if untreated, it states.

John Dart, honorary professor at the UCL Institute of Ophthalmology in the UK, told BBC News that around 150 to 200 people are infected in the UK each year. "Very few" lose their eyes, but "about half" will lose a significant amount of vision, he said.

Acanthamoeba keratitis can make it feel like sand is constantly stuck in your eye

Mason first noticed something was wrong in 2015.

"I started thinking I had a foreign body like sand or grit in my eye that would normally go away when you rub it, but it wouldn't," she said. , according to BBC News.

Symptoms of Acanthamoeba keratitis may include: eye pain, sensitivity to light, blurred vision, and a feeling of something in the eye. The CDC recommends that people talk to a doctor if they experience any of these symptoms.

An ophthalmologist advised Mason to go to the hospital, and doctors diagnosed her with acanthamoeba keratitis and treated it with various medications, eye drops, and three cornea transplants—but all failed.

"It was just a lot of hospital visits, a lot of eye drops, a lot of operations and procedures, and a lot of pain," Mason told UK-based news agency SWNS.

Five years later, the decision was made to remove her left eye and she has had a false replacement since the operation two years ago.

"I do struggle sometimes because my vision on my left side is rubbish, well it's not there. It's quite hard walking down the street when you've got people whizzing by you, and it makes you jump a bit because you don't expect it," she said.