How can tap water cause blindness?

      Contact lenses are convenient, aesthetic, and modern. Millions of people around the world choose them over glasses and feel comfortable. However, this convenience has a dark side that many are not even aware of.

      We are talking about Acanthamoeba keratitis — a severe parasitic inflammation of the cornea that, in advanced cases, leads to blindness. The causative agent — the microscopic amoeba Acanthamoeba — lives everywhere: in tap water, swimming pools, lakes, soil, and even in air conditioning systems. For contact lens users, this amoeba is the main threat.

      Angelina Kazantseva, an assistant at the Department of Ophthalmology named after Academician A.P. Nesterov at the Pirogov University Institute of Clinical Medicine, explains why the disease is so dangerous, who is at risk, and how to protect your eyes.

      Why Acanthamoeba keratitis is so dangerous

      Acanthamoeba keratitis is not a common inflammation. It is an aggressive parasitic process that destroys the cornea from the inside. The amoeba does not just irritate the eye — it literally "eats" the cells of the corneal epithelium, penetrating deeper and deeper.

      The danger of this infection lies in three key features.

      Resistance. Acanthamoeba can survive in conditions that kill most bacteria. It forms cysts — special forms in which it can remain for years, waiting for favorable conditions. Ordinary disinfecting solutions for lenses often do not affect it.

      Aggressiveness. Once on a damaged cornea, the parasite begins to actively invade its layers. The process is rapid, and symptoms escalate quickly.

      Difficulty of treatment. Therapy for Acanthamoeba keratitis is a long and complicated process that can stretch for months. Special, often toxic to the eye, drops are used. In many cases, a corneal transplant is required. Even with timely treatment, irreversible consequences often remain: significant reduction in visual acuity or complete blindness.

      Why the disease affects contact lens wearers

      Contact lenses themselves are not a source of infection. However, they create ideal conditions for the amoeba to enter the eye, settle, and begin its destructive work. The lens plays three fatal roles in this process.

      The first role is a "bridge." The lens is a foreign body that can mechanically transfer the pathogen from hands or from the solution directly onto the surface of the eye. A single drop of water with the amoeba is enough — and it is already on the cornea.

      The second role is a "greenhouse." A closed, warm, and moist space forms between the lens and the cornea — an ideal environment for the parasite to multiply.

      The third role is "gate." Even with careful wear, microscopic damage inevitably occurs on the cornea. Especially if the lenses are improperly fitted or worn longer than recommended. These micro-damages are the entry gates for infection.

      Main causes of infection: a reminder for every lens user

      Angelina Kazantseva highlights three main reasons that are highly likely to lead to Acanthamoeba keratitis.

      The first reason is water. This is an absolute taboo. The amoeba lives in water, so it is strictly forbidden to:

      wash, swim, or take a shower while wearing lenses;

      rinse lenses or the container with tap, bottled, or any other non-sterile water;

      rinse the container with tap water.

      Even a drop of water from the sink can contain Acanthamoeba. Risking your vision for a minute's habit is unacceptable.

      The second reason is violation of wearing and hygiene regimen:

      sleeping in lenses not designed for that (except for special models for overnight wear); oxygen access to the cornea decreases during sleep, increasing the risk of damage;

      exceeding the wearing period — for example, using monthly lenses longer than the specified period;

      using expired solution or reusing it;

      insufficient cleaning — simply pouring solution over the lenses without rubbing them with your fingers is not enough.

      The third reason is ignoring the first symptoms.

      Any discomfort is a warning signal. But there are symptoms that require an immediate visit to the doctor:

      severe, intolerable pain in the eye, much more pronounced than with ordinary conjunctivitis;

      redness that does not go away after removing the lenses;

      photophobia and pronounced tearing;

      the sensation of a foreign body, sand in the eye.

      If at least one of these manifestations appears, the lenses must be removed immediately, and you should urgently consult an ophthalmologist. And be sure to inform the doctor that you wear contact lenses.

      How to make lens wear safe: iron rules

      Preventing Acanthamoeba keratitis is not difficult, but it requires discipline. Angelina Kazantseva recommends adhering to several unbreakable rules.

      Wash your hands with soap and dry them with a lint-free towel before any contact with lenses. This is the first and main protection against introducing infection.

      Use only fresh sterile multi-purpose solution for cleaning and storing. No water — neither tap, nor filtered, nor bottled. The lens solution is not designed to kill Acanthamoeba, but it creates an environment unfavorable for its growth if used correctly.

      Change the lens storage container at least once a month. An old container is a breeding ground for bacteria and amoebas, even if it looks clean.

      Strictly adhere to the wearing regimen: daily, flexible, or extended — only as prescribed by the doctor. Do not experiment with the duration.

      Remove lenses before any contact with water. This applies to showers, baths, swimming pools, open water bodies, and even washing your face.

      Regularly undergo examinations by an ophthalmologist — at least once a year, even if you have no complaints. The doctor may notice microscopic changes in the cornea that you do not feel and adjust the wearing regimen.

      In short: what to remember

      Acanthamoeba lives in water — any water.

      Water and lenses are incompatible.

      Do not rinse lenses and containers with water.

      Do not wash, swim, or take a shower in lenses.

      Adhere to wearing periods and solution replacement.

      Change the container every month.

      At any pain, redness, or discomfort, remove lenses and see a doctor.

      Acanthamoeba keratitis is a rare but extremely dangerous disease. It spares neither those who have worn lenses for many years nor newcomers. But it is almost 100 percent preventable if simple rules are followed.

      As Angelina Kazantseva reminds us, eye health is not only comfort today but also vision tomorrow. Treat lenses as a medical device, which they are. Do not skimp on solutions, do not violate the regimen, and never — never — allow water to touch the lenses or the container. Vision is worth being careful.