A teenager has been left battling chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis (ME), after a parasite burrowed into her eye.
Skye Wheeler, 19, from Cambourne, Cornwall, endures unrelenting exhaustion and excruciating pain that has left her confined to her small bedroom.
According to the Daily Mail, Ms Wheeler became unwell at 14 when a parasite burrowed into her cornea and ate away at her eye, where the microorganism is still "sleeping". The bug caused the teenager to develop an infection, known as Acanthamoeba keratitis.
She said: "I was told it is found in tap water. The ultimate mistake was a droplet of water between my eye and my contact lens. It could blind me or even kill me one day.
"My life has been ripped to pieces and then burnt down into nothing but ash and smoke."
Although CFS' cause is unclear, the condition has been linked to infections, with some doctors reporting on cases that appeared to be caused by Acanthamoeba keratitis.
Ms Wheeler is speaking out to coincide with Severe ME Awareness Day.
"I have a parasite in my eye"
Speaking of her condition, Ms Wheeler said: "I have a parasite in my eye. The Acanthamoeba burrowed into my cornea and ate away to create snail trails around my eye.
"Despite years of treatment, I still have this parasite in my eye.
"I am told that it is dormant. It goes into this stage to protect itself, picture it curling into a ball.
"We will never be able to tell whether it is dead or not or if and when it may reawaken so I have to live with the feeling of never knowing."
"The fatigue is like a thousand bricks being tied to your body"
Ms Wheeler began experiencing ME symptoms just one month after coming off medication to treat an eye problem.
Speaking of how misunderstood ME is, she said: "The fatigue is like no other.
"I actually wish there was another name for it. There is nothing I would give more than to transfer my symptoms to another person for just an hour.
"The fatigue we feel is like a thousand bricks being tied to your body. You can't muster up the energy to put on foot in front of the other.
"You can't get dressed and ready for the day without a blackness descending over your eyes. You can't carry a conversation let alone even speak.
"The bottom of the line is that there is no energy there in the first place to channel through your body to all the right places. The only thing you can do is lie and exist."
Ms Wheeler's condition has forced her to watch while her friends pursue adventures while she is housebound.
She said: "I lay in the dark because of light sensitivity alone and waiting for someone to return home and take me to the toilet.
"My bed is my world. My bed is my support. It has seen me through endless days of torturous pain, fatigue and inner turmoil."
"It can feel like a constant flu"
A spokesman from the ME Assocation said: "It is an invisible illness. When you see us, we might not always look ill, but when our symptoms flare, the effects are obvious.
"It can feel like a constant flu, the smallest exertion can floor us, our bodies are painfully sore, restful sleep eludes us, light and noise are intolerable, and 'brain fog' causes confusion.
"ME remains a hidden disease. There is no known cure and no effective treatment - and it can lead to greater functional impairment than multiple sclerosis or cancer.
"The most severe sufferers are often the most hidden. A lot of people give up and their families are left fighting, so they can't raise awareness. There's a higher risk of suicide with ME sufferers.
"People find it hard to understand, with the medical advancements, how something like this can happen in this day and age."