A student was forced to stay awake for days on end to stop a parasite eating her eyeball.
Jessica Greaney, 18, contracted rare disease Acanthamoeba Keratitis after a drop of water splashed on her contact lens.
The first-year English student at Nottingham University said her left eye swelled to the size of a "huge red golf ball".
Doctors ordered Ms Greaney to apply eye drops every 10 minutes as her cornea was being "eaten away from the inside by the parasite".
Ms Greaney initially thought she had an eye infection, but doctors eventually diagnosed her after clamping open her eye and scraping off a layer with a scalpel.
The parasite apparently survived in the area between the lens and her eye.
Describing her ordeal, Ms Greaney told student newspaper The Tab: "My eye was bulging, and it looked like a huge red golf ball - it was extremely painful."
The student, who is originally from Birmingham, said being kept awake for four days was "torture".
"Even if I had managed to nod off, I could only get a couple of minutes' sleep before I was woken again," she said.
"This parasite was still eating my eye and even worse, my immune system was shutting down because of my lack of sleep."
Ms Greaney is now on the road to recovery but she is still required to take drops and visit her doctor for regular check-ups.
"It's a slow process, but my sight is almost back to normal and I'm hoping to get the all-clear from the doctor within the next couple of weeks," she said.
What is Acanthamoeba Keratitis?
- Acanthamoeba Keratitis is an infection of the cornea
- It is caused by a microscopic organism called Acanthamoeba
- This is usually found in water (lakes, oceans, rivers as well as domestic tap water)
- It is most common in people who wear contact lenses (85% of cases)
- Moorfields Eye Hospital say the infection can be "extremely painful"
- If left untreated, the disease can cause long-term vision damage
How to avoid catching the disease
Poor contact lens hygiene is one of the main causes of Acanthamoeba Keratitis - here's some important things to avoid:
- Swimming or showering in contact lenses
- Using unwashed hands to handle lenses
- Rinsing or storing lenses in water