The case-control study, published in Ophthalmology, identified several: factors that increase risk from this pathology, a type of microbial keratitis that causes inflammation of the cornea (the transparent protective outer layer of the eye) and requires intensive care and even a corneal transplant, leaving serious sequelae in vision. Among the habits that can increase the likelihood of suffering from it are lens reuse or use during night or in the bathroom.

“In recent years, we have seen increase in keratitis by Acanthamoeba in the UK and Europe, and although infection remains rare, it is preventable and requires a public health response,” said lead author Professor John Dart, of the UCL Institute of Ophthalmology and Moorfields Eye Hospital NHS Foundation Trust.

“Contact lenses are generally very safe, but are associated with a small risk of microbial keratitis, usually caused by bacteria, which is the only vision-threatening complication of wearing contact lenses. With about 300 million people worldwide wearing contact lenses, it’s important that people know how to minimize their risk of keratitis,” Dart added.

Vision loss from microbial keratitis is rare, but Acanthamoeba, although a rare cause, is one of the most serious, accounting for about half of contact lens wearers who experience vision loss after keratitis. 90% of cases are associated with avoidable risks, although infection remains rare, affecting less than 1 in 20,000 contact lens wearers a year in the UK.

Acanthamoeba keratitis causes the front surface of the eye, the cornea, to become sore and inflamed as a result of Acanthamoeba infection, a cyst forming microorganism. The most severely affected patients (a quarter of the total) end up with less than 25% vision or become blind after the disease and face prolonged treatment. Overall, one in four affected people need a corneal transplant to treat the disease or restore vision.

For the study, the researchers recruited more than 200 Moorfields Eye Hospital patients who completed the survey, including 83 people with the condition, and compared them with 122 participants attending an eye care clinic with another condition, acting as a control group.

People who wear reusable soft contact lenses (such as monthly ones) are 3.8 times more likely to develop Acanthamoeba keratitis, compared to people who wear disposable lenses every day. Bathing with contact lenses increases the chance by 3.3 times, while wearing contact lenses at night increases the likelihood by 3.9 times. Among everyday disposable contact lens wearers, reuse increases the risk of infection. In contrast, having a recent lens examination by a healthcare professional lowers the risk.

A recent study led by Professor Dart found that this type of keratitis is increasing in prevalence in the UK. Reviewing incident data from Moorfields Eye Hospital from 1985 to 2016, he and his team found an increase from 2000-2003, when it rose from eight to 10 cases per year to between 36 and 65 cases per year at the end of the period. .

“Previous studies have linked Acanthamoeba keratitis with contact lens wear in hot tub, pool, or lake, and here we’ve added showers to that list, emphasizing that exposure to water should be avoided when wearing lenses. Public swimming pools and coastal authorities can help reduce this risk by advising against swimming with contact lenses,” said Associate Professor Nicole Carnt, of the UCL Institute of Ophthalmology and Moorfields Eye Hospital, and first author of the study.

In Dart’s opinion, “a contact lens case should include information about risk prevention, even something as simple as a contact lens sticker. ‘no water’ in any case, considering that many people buy their lenses online without talking to a healthcare professional«. In addition, the lead author of this study cautions that taking basic hygiene measures while wearing contact lenses can be very helpful in preventing infection,” such as wash and dry hands thoroughly before wearing contact lenses.