Wearing contact lenses while showering or swimming (or sleeping with them on) may seem like a harmless way to save time.
But these common habits increase the risk of painful eye problems and even blindness, experts warned.
The main concern is a microscopic parasite often found in water, including tap water, called acanthamoeba keratitis.
The insect is normally harmless, but wearing contact lenses can create microscopic tears in the front of the cornea, through which acanthamoeba can enter.
They then multiply and cause eye pain, redness, blurred vision, sensitivity to light, and watery eyes. In the worst case, it can cause blindness.
Acanthamoeba can enter the eye while bathing or showering, and if contact lenses are worn during these activities, the chances of infection increase dramatically.
Even leaving contacts in overnight can increase the risk.
This is because small amounts of acanthamoeba can be transferred to the eyes if a person washes their hands and then touches their face.
Nina Wang, 30, from London, fell victim to the parasite while on holiday in Bali in July 2019.
At first, Ms. Wang only felt irritation and stickiness, but her symptoms progressed to discomfort, pain, and unbearable sensitivity to light. Two days later, on July 16, 2019, he was admitted to the hospital.
Wearing contact lenses during sleep creates the perfect environment in which acanthamoeba can thrive.
Lens manufacturers and opticians make these risks clear, but hundreds of Britons suffer from the infection each year, according to the College of Optometrists.
Meanwhile, an estimated 1,500 Americans suffer from it each year, according to The Cleveland Clinic.
Nina Wang, 30, from London, fell victim to the parasite while on holiday in Bali in July 2019.
The businesswoman, who has worn contact lenses since she was 11, began to feel irritation in her right eye, but assumed her symptoms were just mild conjunctivitis and would go away on their own.
“I’ve had to deal with a lot of irritations that are normally insignificant, but they got worse the next day,” he told MailOnline.
She admitted that she occasionally fell asleep with her contact lenses in, alternating between monthly and daily types to limit the amount she had to carry on her six-week trip.
At first, Ms. Wang only felt irritation and stickiness, but her symptoms progressed to discomfort, pain, and unbearable sensitivity to light.
The photograph (left) shows the scar blocking the pupil and vision, and the photograph on the right shows how the specialized treatment eliminated the scar in the pupil area while significantly reducing myopia (nearsightedness).
Two days later, on July 16, 2019, he was admitted to the hospital.
When her symptoms worsened, she sought medical help at a local hospital in Bali, where she was diagnosed with microbial keratitis.
She was given antibiotics and medical staff recommended she travel to Jakarta for more specialized treatment, but she decided to stay in Bali.
Ms. Wang followed the hospital’s initial instructions, which included wearing an eye patch, avoiding sunlight, and using prescribed eye drops.
Returning to the UK three weeks later on August 4, Ms Wang sought further care at Moorfields Eye Hospital, where specialists recognized the infection.
Over time, the infection caused a vision-blocking scar to develop in his right eye; however, he continued to wear his contact lenses for 18 months.
Finally, he turned to Professor Dan Reinstein, a specialist ophthalmic surgeon at London Vision Clinic, in November 2020.
He underwent laser eye surgery that helped him regain 90 percent of his vision.
McCasland was forced to stop working at the cafe as a result of the infection. The pain, which had persisted for a month and a half, made it difficult for him to work, as did the loss of vision in his left eye, which caused changes in depth perception.
McCasland has lost vision in his right eye and is awaiting an expensive transplant that has only a slim chance of restoring his breathing.
Ms Wang said: “This has been a multi-year process, with a lot of time and money spent correcting the scar, and Dan has done an incredible job.”
He added that his vision is now “completely manageable.”
But not everyone is as lucky as Ms. Wang: for some the infection leaves them permanently blind.
Brooklyn McCasland, 23, from Texas, US, lost all vision in her right eye after contracting the parasites, which also live in fresh and salt water, while swimming with her contact inside.
The doctors first told the barista that he just had sand in his eye. They later blamed a common infection and gave him eye drops and antibiotics.
But the pain continued and the outer layer of his eye began to cloud, which his doctor assumed was damage from an infection.
Mrs McCasland is now blind in her right eye and is awaiting an expensive corneal transplant which has only a slim chance of restoring her sight.
In May 2019, Emily Kelleher, a high school English teacher in Massachusetts, felt like she was being stabbed in her left eye with a “knife or ice pick”; she had also been infected with the parasite.
Ms. Kelleher’s eye under the microscope (pictured) at her doctor’s office revealed the presence of acanthamoeba parasites.
His doctors told him he probably contracted it when the parasites got into his eye while he was showering with contact, something he used to do every day.
Last year, Rachel Prochnow, a lifestyle writer based in Austin, Texas, went blind in her right eye after showering with her contact lenses in.
He had always been careful about his eye care and had worn contact lenses since he was 12 years old.
Prochnow says she always took them out at night, cleaned them well, and threw away her contact lens cases regularly, making sure everything was sterilized.
But she admits she didn’t realize that showering, swimming or getting into a hot tub with her contact lenses in could leave her vulnerable to infection.
If acanthamoeba keratitis is caught early, doctors can easily treat it with eye drops.
Tina Patel, contact lens optician at Feel Good Contacts, stressed that the best way to avoid infections is to maintain a proper lens care routine.
She told MailOnline: ‘If you wear two contact lenses weekly or monthly, make sure you remove, clean and store them properly every night before you go to sleep.
Ms. Prochnow first noticed something was wrong when she felt a little itchy eye and sensitivity to light. Soon, he felt excruciating pain and could not see anything except light and hand movements.
“Contact lenses should never be worn in swimming pools, hot tubs, and showers.”
He warns that even any water residue left on your hands before inserting lenses could be enough to cause acanthamoeba keratitis.
Professor Reinstein told MailOnline: “Soft contact lenses are more prone to acanthamoeba keratitis, due to the higher water content that can attract and harbor microorganisms.
“In addition, extended wear lenses, which are often worn overnight, limit oxygen to the cornea and can trap contaminants in the eye for prolonged periods, increasing the risk of infection.”