Medics forced a student to stay awake for a week to prevent a parasite from burrowing into her eyeball.
Jessica Greaney, 18, had eyedrops administered every ten minutes for seven days in a row after doctors found a small worm-like creature in her left eye from a contact lens.
Miss Greaney, a first-year English student at the University of Nottingham, was told she got the parasite - acanthamoeba keratitis - in her eye after a drop of tap water splashed on her contact lens.
At first, she thought she had an eye infection as her eyelid was dropping, which was then mis-diagnosed as an ulcer by doctors.
She said: "But, by the end of the week, my eye was bulging, and it looked like a huge red golf ball. It was swollen, and extremely painful, and they admitted me into hospital.
"I had an intensive treatment of eyedrops every ten minutes because my cornea was being eaten away from the inside by the parasite."
Miss Greaney, originally from Birmingham, was finally diagnosed with the parasite after doctors clamped open her eye and scraped off a layer with a scalpel, which was then sent away for testing.
She said: "Apparently, all water has tonnes of different types of bacteria and the acanthamoeba just happens to be one of them. One of my contact lenses got contaminated, and the parasite survived in the area between the lens and my eye."
If untreated, the parasite causes sight problems and paralysis or even death as it eats its way through the eye and into the spinal cord.
Speaking to student newspaper The Tab, she said: "They had to keep me awake for a week. It was torture - she had to hold my eye open and squirt a few droplets in.
"Even if I had managed to nod off, I could only get a couple of minutes' sleep before I was woken again. This parasite was still eating my eye and even worse, my immune system was shutting down because of my lack of sleep."
Miss Greaney has been wearing contact lenses for just two years and had no idea that she could contract an eye parasite from normal water.
She said: "I want to raise awareness about this parasite and tell people they need to be very careful with their contact lenses.
"If so much as a droplet of water gets into contact with the lens, problems can occur. I got my infection by just leaving my contact lenses near my sink, in a glass of solution."
Miss Greaney, who was admitted to hospital on March 26, still has to continue taking 21 droplets a day.