The parasite, called acanthamoeba, lives in water and enters through microscopic tears in the eye.
They are about 5,000 times smaller than the width of a human hair.
Brooklyn is now waiting for an expensive transplant that only has a small chance of restoring her sight.
Doctors thought the pain which ‘felt like glass’ was caused by an infection, but Brooklyn’s vision went blurry several weeks later.
She said: ‘They were still just shooting in the dark which was really frustrating. I remember praying.’
After travelling four hours to the specialist, she was diagnosed with acanthamoeba keratosis, MailOnline reports.
Brooklyn said: ‘It was a shock but also a relief to have everything answered.
‘For so long being misdiagnosed and not knowing what it is and it getting worse and being in pain.’
If caught early enough, doctors can prescribe eye drops which can kill the parasites.
In around 40% of cases doctors have to perform surgery, which involves scraping the outside of the eye to remove the parasites and repairing the area through transplant.
Brooklyn is urging contact wearers to be careful using them in water after being told by doctors ‘it is not a big deal’ to shower with them in.
She said: ‘That upset me, especially after finding out I did have it.’
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