'A parasite was eating my eyeball'

Her right eye was still slightly bigger than usual as it started to heal

Jessica Greaney thought she had a relatively minor infection but the 19-year-old actually had a parasite eating her eyeball.

The bug, called Acanthamoeba Keratitis, affects around one in 50,000 contact lens wearers in the UK each year.

The student's treatment meant she had to stay awake for days while she had eye drops put in every half an hour.

This is Jessica's story

"My eye felt like there was something in it and it kept closing.

"I booked a doctor's appointment, but throughout the day it got even worse so one of my friends decided to take me to the hospital and they diagnosed it as an ulcer on the eye.

"Then a week later, at my check up, they decided it was the Acanthamoeba and I had to be admitted to hospital straight away.

"I was on eye drops every half an hour throughout the day and night for four days and then that obviously meant that I couldn't sleep.

"That just meant I had no energy throughout the day. I found it hard to eat food and my immune system began to shut down.

Her eye during the infection

"Four nights of not being able to sleep sounds like torture and it is. It's really heartbreaking and hard to go through.

"There was a moment when I asked the doctor if I was ever going to get better, but it was really hard for them to say.

"But they said it was a very rare chronic serious infection. I remember looking through the one eye and not being able to see anything because everything was completely blurry.

"I could just see colours rather than actual things.

"The infection is picked up from water, but it's definitely more common to get it from contact lenses because if water comes into contact with the lenses, when you put that lens in your eye it has nowhere to go.

"That's when it can start eating through the eye, which is what causes all the pain.

Jessica after leaving hospital
Image caption Jessica after she left hospital

"I don't want people to have the misconception it's just if you're not clean with your lenses.

NHS advice for contact lens users

    • Avoid wearing contact lenses in the shower or when swimming
    • Don't sleep in lenses (unless your optician has told you to)
    • Wash and dry your hands before touching your lenses
    • Don't leave them in water overnight or spit on them when they are dry or fall out
    • Don't over-wear them

"I was really, really careful with my lenses, I'm actually quite known with my friends for being ridiculously over clean with them, but I kept my contact lenses by the sink in my room.

"I know so many people that shower in them or swim in them. It's just not worth it.

"The amount of pain you have to go through is absolutely ridiculous. That's not something you should risk.

"I wouldn't change a single second of my treatment because that's what made me get so much better.

"Although it's hard, it is worth it in the end because I'd rather go through four nights of not being able to sleep than not being able to see for the rest of my life.

"Now I'm feeling a lot better and there's no redness in my eye and no pain.

"I'm still on lots of eye drops - twenty a day now. That seems like a lot but it's a lot less than I was originally on."

Here comes the science

Acanthamoeba Keratitis is an infection of the cornea - the clear 'window' at the front of the eye.

It's caused by a living single-celled parasite (a bug that lives on other organisms) and can lead to permanent sight damage or blindness if it comes into your eye.

The bug is otherwise harmless to humans. We come into contact with them when we wash, swim and drink water.

It can affect people with cornea injuries as well as those who wear contact lenses.

But the condition can be hard to diagnose because the symptoms are similar to other infections.

Follow @BBCNewsbeat on Twitter, BBCNewsbeat on Instagram, Radio1Newsbeat on YouTube and you can now follow BBC_Newsbeat on Snapchat