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What lies beneath

Optometrist, Ceri Smith-Jaynes, on the dangers of swimming in contact lenses

18 May 2017 by Ceri Smith-Jaynes

Swimming is a very popular sport and a really good all-round exercise for the body. With summer holidays firmly on the way I’m sure, like me, you will be venturing back into the water. And I highly recommend it if your joints don’t like you running. My tip for fitness is to vary your stroke and pace and if you’re setting a number of lengths you wish to do, count them down rather than up.

I remember as a child I was always happiest under water. My vision would go foggy if I swam without goggles for a long time. I now know this is because the front part of my eye, my cornea, had swollen with water. Salt water or swimming pool water irritates the eyes and will make them dry and red after swimming. Lubricant eye drops, also known as artificial tears, can soothe the eyes and you can buy these in most opticians and pharmacies. If you find using eye drops difficult, read our helpful tips from optometrist, Dr Ian Beasley.

Of course, it’s better not to create the irritation in the first place by wearing well-fitted goggles.

Some creatures you’ll never see coming

Swimming-related eye infections are possible in anyone but contact lens wearers are at far greater risk than the rest of the population. The worst culprits for infections are bacteria, such as Pseudomonas aeruginosa and an amoeba known as Acanthamoeba. Both of these can cause very painful infections which result in sight loss or even losing an eye after months of unsuccessful treatment. A contact lens can trap one of these microscopic critters against the eye and contact lens wearers are also more likely to have a miniscule scratch on the eye, which is an open door for said critters to penetrate the eye’s surface. Fortunately, these types of infections are rare but swimming in contact lenses does greatly increase this risk.

Doesn’t the chlorine kill the bugs though? Not all of them: Acanthamoeba exists in two forms in its life cycle, the trophozoite form and the cystic form. The trophozoites are single-celled organisms which have that classic amoeba look: blobby brainless things which feed on other cells such as bacteria and cornea cells. The cysts are microscopic, dormant, double-walled capsules that can resist chemical disinfection and medical treatments like eye drops. High concentrations of chlorine do not kill the amoeba cysts. In fact the cysts can proliferate in the pool’s filter so the filter must be cleaned regularly by reversing the flow.

What can I do? I can’t swim in my glasses

Understandably, you do need to see which child is yours and if you’re swimming in the sea, a lake or a river, it’s great to be able to see the detail of underwater life beneath you. It’s safer not to swim in contact lenses at all; if you absolutely have to, the British Contact Lens Association (BCLA) advice for swimmers is to use daily disposable lenses with a well-sealed pair of goggles or mask and discard the lenses immediately after you finish swimming. If in doubt, read our advice for contact lens wearers.

There are other options though: your optometrist can advise you on prescription dive masks and goggles and you can even get wrap-around goggles in some prescriptions. Some people are suitable for orthokeratology (ortho-K). This is a type of rigid contact lens that gently re-shapes the eye and you wear it overnight, removing it on waking. During the day, short-sightedness (myopia) is corrected so you don’t need glasses or contact lenses for swimming.

For more patient information and advice videos, explore our For patients section.

Ceri Smith-JaynesCeri Smith-Jaynes is OT’s Multimedia Clinical Editor and is an optometrist in independent practice in Lancashire