According to a study led by UCL and Moorfields researchers, people who wear reusable contact lenses are almost four times more likely to develop a rare sight-threatening eye infection than those who do not.
Reusing lenses, wearing them overnight, or using them while in the shower are just a few of the factors that increase the risk of Acanthamoeba keratitis (AK), according to a case-control study that was published in the journal Ophthalmology.
A type of microbial keratitis (corneal infection) that causes inflammation of the cornea, the clear outer layer of the eye, is AK.
Professor John Dart, the lead author, from the Moorfields Eye Hospital NHS Foundation Trust and the UCL Institute of Ophthalmology, stated: “Acanthamoeba keratitis has become more prevalent in the UK and Europe in recent years. Even though the infection is still rare, it can be stopped and needs a response from public health.
“The only sight-threatening side effect of contact lens use is microbial keratitis,” which is most frequently brought on by bacteria and is associated with a small risk of contact lens use. Given that an estimated 300 million people wear contact lenses worldwide, it’s critical that people understand how to reduce their chances of getting keratitis. ”
In patients with otherwise healthy eyes in northern hemisphere nations, contact lens use is now the main contributor to microbial keratitis. Even though Acanthamoeba is a rare cause of keratitis caused by microorganisms, it is one of the most severe and accounts for about half of all cases of sight loss experienced by contact lens wearers. Even though the infection is still rare—less than 1 in 20,000 contact lens wearers in the UK get it every year—90% of AK cases are linked to risks that can be avoided.
Because of an infection with the cyst-forming microorganism Acanthamoeba, AK leads to the front surface of the eye, the cornea, becoming painful and inflamed. The patients who are most severely affected (about 25% of the total) eventually lose more than 25% of their vision or go blind as a result of the illness and require extensive care. 25% of those with the condition need a corneal transplant to treat it or get their vision back.
In order to conduct the study, the researchers gathered over 200 Moorfields Eye Hospital patients to participate in a survey, including 83 with AK. Then, they compared these people to a control group of 122 people with different health problems who went to eye care clinics.
Reusable contact lenses wearers (such as monthly wearers) had a 3.8 times higher risk of developing AK compared to daily disposable lens wearers. Wearing lenses overnight increased the odds of AK by 3.9 times, while showering with lenses in by 3.3 times. The risk of infection increased when daily disposable lens wearers reused their lenses. The risk was lower if you recently had your contact lenses checked by a medical professional.
The researchers figured that between 30 and 62% of cases in the UK and possibly in many other countries could be avoided if people switched from reusable to daily disposable lenses.
According to a recent study conducted under Professor Dart’s direction, AK is becoming more common in the UK. By looking at data from Moorfields Eye Hospital from 1985 to 2016, he and his team found that the number of cases rose from 8 to 10 per year in 2000–2003 to between 36 and 65 per year at the end of the study period.
Associate Professor Nicole Carnt, the first author, from Moorfields Eye Hospital, UNSW, Sydney, and the UCL Institute of Ophthalmology, said: “Here, we add showers to the list of places where wearing reusable contact lens has been linked to AK in previous studies, underscoring the need to avoid exposure to any water while wearing lenses. “By cautioning against swimming with contact lenses, public pools and coastal authorities could help lower this risk.”
Prof. Dart went on to say, “Since many people buy their contact lenses online without consulting a doctor, the packaging should include information on how to keep the lenses safe and avoid risks. This could be as simple as putting “no water” stickers on each case.”
“Simple steps like washing and drying your hands completely before putting in your contacts can go a long way toward keeping you from getting an infection.”
The study was paid for by grants from the NIHR Moorfields Biomedical Research Centre, the Moorfields Eye Charity, and Fight for Sight.
