Contact lenses should never be exposed to any water source, including tap water, while showering, swimming, or engaging in other water activities like using a hot tub. This restriction is due to the inherent risk of severe eye infection from waterborne microorganisms. The primary danger comes from organisms naturally present in water, which can become trapped against the eye by the lens, leading to potentially sight-threatening complications.
The Core Risk: Why Water and Lenses Don’t Mix
The danger of water exposure is rooted in the physical properties of soft contact lenses. Soft lenses are composed of hydrogel or silicone hydrogel materials, which are hydrophilic, meaning they absorb and hold water to remain soft and permeable. This absorption capacity allows the lens to act like a sponge. When exposed to non-sterile water sources like tap water, the lens quickly absorbs any microorganisms present.
While tap water is treated to be safe for drinking, it is not sterile and contains various microscopic organisms, bacteria, and minerals. The amoeba Acanthamoeba is a particularly dangerous organism commonly found in tap water and other water sources. Once the lens absorbs contaminated water, the lens material holds the microbe directly against the cornea.
The presence of the lens creates an environment for these organisms to adhere to the eye’s surface, especially if the cornea has minor abrasions. Water can also cause soft lenses to swell and change shape, leading to discomfort or scratching the corneal surface, which provides an entry point for germs. Even without Acanthamoeba, other bacteria like Pseudomonas aeruginosa or Staphylococcus can cause serious infections when trapped by the lens.
Understanding Acanthamoeba Keratitis
The most severe consequence of exposing contact lenses to water is Acanthamoeba keratitis (AK). AK is a rare but highly destructive parasitic infection of the cornea caused by the Acanthamoeba amoeba. This amoeba damages the cornea, the clear front surface of the eye, leading to significant vision impairment.
Symptoms include severe eye pain, excessive tearing, eye redness, and intense sensitivity to light. The pain may be disproportionate to the physical appearance of the eye. Patients often report a sensation that something is constantly stuck in the eye, which cannot be relieved. Blurred or clouded vision also occurs as the infection progresses and causes inflammation or scarring on the cornea.
Acanthamoeba keratitis is difficult to treat, often requiring specialized topical antiseptic drops for a prolonged period, sometimes for six to twelve months or longer. The difficulty arises because the amoeba can transform into a protective cyst form, which is highly resistant to standard antimicrobial treatments. If the infection is not diagnosed and treated quickly, it can lead to permanent vision loss and may require a corneal transplant.
Safe Practices for Contact Lens Wearers
Maintaining strict hygiene is the most effective defense against waterborne eye infections. Contact lenses should only be cleaned, rinsed, or stored using fresh, sterile disinfecting solution recommended by an eye care professional. Never use tap water, distilled water, or saliva for any part of the lens care process, as none of these are sterile.
Avoid the practice of “topping off” old solution, where new solution is merely added to the existing solution in the case. The solution must be completely discarded and replaced with a fresh amount every time the lenses are stored. Lenses must be removed before showering, swimming, or entering a hot tub. If water exposure accidentally occurs, the lenses should be immediately removed and thoroughly disinfected overnight before being worn again.
The lens case requires diligent care to prevent it from becoming a breeding ground for microbes, as cases are often the most contaminated part of the lens system. After removing the lenses, the case should be emptied, rinsed with fresh solution, and left to air dry upside down with the caps off. The contact lens case should be replaced entirely every one to three months to ensure a clean storage environment.