A 23-year-old student has lost an eye to flesh eating amoeba after not taking out her contact lenses for six months. Health officials say this case can serve as a harsh reminder as to why we regularly change and clean our lenses.

Taiwanese student Lian Kao was diagnosed with bacterial keratitis - a condition in which a microbial parasite burrows through the eye to feed on the retina directly - and has subsequently lost an eye due to her own negligence.

Naturally, the question on everyone's mind is, after weeks or even months of infection, how did Kao not notice an amoeba colony was gnawing on her eye?

According to Wu Jian-Liang, director of ophthalmology at Wan Fang Hospital, despite how painful it sounds, an infection of the amoebae Acanthamoeba is actually rather subtle, only causing slight pain, red eyes and blurred vision over the course of weeks or months. It even can be mistaken for an allergic reaction, especially during summer months.

Starved of oxygen from wearing contact lenses for so long, Kao's eyes were also likely less sensitive than they are naturally.

"Contact lens wearers are a high-risk group that can easily be exposed to eye diseases," Jian-Liang said, according to the Daily Mail. "A shortage of oxygen can destroy the surface of the epithelial tissue, creating tiny wounds into which the bacteria can easily infect, spreading to the rest of the eye and providing a perfect breeding ground."

According to the US Environmental Protection Agency (EPA), Acanthamoeba keratitis can be treated, but only during early stages when the infection is still largely trapped in the cornea - the protective film that covers the front of the eye. A cornea can be transplanted, but once a parasitic cell breaks into the actual eye, the irreversible damage has already been done.

While this kind of infection is rare and mainly seen among people who neglect proper contact hygiene, the US Centers for Disease Control and Prevention (CDC) has stayed vigilant for outbreaks of this condition, especially in instances where a contact solution fails to protect users entirely.