I was a water polo player back in college. Every evening after practice, my vision became extremely hazy and my eyes blood-shot red and irritated. This was before my ophthalmology days so I didn’t think much about it, but the pool water was actually causing some short-term damage to my eyes.
The chlorine used to keep pool water clean and its byproducts will cause your eyes to be irritated. But chlorine isn’t the only factor: pH and the tonicity of the water also will affect your eyes. While there are no treatments to make this disappear after swimming, there are ways you can help encourage healing.
Of course, you can’t get rid of the chlorine or other disinfectant in the pool. Otherwise pools would be just gross! So get on your chemistry cap as we learn exactly how pool water will affect your eyes.
Pool Water Can Irritate the Eyes
The irritation and blurry vision you get after swimming is actually due to the surface of your eye being damaged from the pool water.
Our cornea is one of the most sensitive structures in our body. To protect the cornea, there is a thin layer of cells called epithelium that sits on the surface. When this layer is intact, our eyes are comfortable.
But after exposure to pool water, this layer can become damaged. This causes your eyes to burn.
Pool water can also irritate the white part of the eye called conjunctiva. As this part of the eye gets irritated, it becomes red.
Thus, with pool water you can have burning and red eyes.
But pool water can also cause your vision to become blurry or hazy. Differences between the pool water and your eye can cause swelling in your corneas. This can change and blur your vision.
So why does this happen?
Why Can Pool Water Damage The Eyes
Pools are artificial bodies of water where swimmers of all ages congregate. And who knows what sort of contaminants those swimmers will bring into the pool…
So of course, pools must be kept clean to prevent the pool from being an infection risk. This is done with chemicals. Chlorine is one of the most common chemicals used to keep the pool clean.
What Pool Chlorine Does on the Eyes
Chlorine is a known eye irritant. Exposing the cornea to water with chlorine will cause irritation to the epithelium on the cornea. But simple exposure to chlorine isn’t the full picture.
When chlorine reacts with the “stuff" in the pool, it forms a new chemical by-product. The technical names for two of the more important of these chemicals are chloramines and trihalomethanes. These chemicals escape the pool through the air. When you walk into an indoor pool and you notice a chlorine smell, these chemicals are what you are actually smelling.
But these chemicals are also well known as eye irritants. In fact, you don’t even need to be swimming to develop irritation from these chemicals. People who work in indoor pools, such as lifeguards, are at a high risk of developing burning red eyes from these chemicals in the air.
But before these chemicals are released in the air, these chemicals exist in the water as well. Like chlorine, chloramines and other by-products will contribute to burning eyes after swimming. This is especially the case if the concentration of these are high in the water. How can the concentration be high? The amount of chlorine in the pool, the pH and temperature of the water and water circulation all effect the levels. Poor ventilation, such as at an indoor pool will also cause the levels to rise both in and out of the water.
So chlorine and its byproducts will irritate the eyes; but this isn’t everything that will affect the eyes.
pH of the Pool Matters
pH measures how acidic of an environment something is. The middle of the pH scale is 7.0. If we have PURE water, we have a pH of 7.0.
The normal pH of the cornea is approximately 7.4. If you add something to the cornea which has a different pH, it will slightly shift the pH on the cornea. If there is too big of a difference between the pH, it will be irritable and cause burning of the eyes.
There is a small range that the eye can tolerate without much issue. And in fact, the eye can also tolerate a slightly more acidic pH (below 7.4) than it can an alkaline pH (above 7.4). Because of this, many artificial tear eye drops have a pH range between 6.9 and 7.4.
An optimal pH for a swimming pool is also 7.4. This keeps the pH in the best range for the human body. If the pool develops too high or too low of a pH, this can irritate the eyes.
Lastly, About Pool Tonicity
There is a difference between sea water and freshwater. The biggest one is how much salt is in the water. Sea water has much higher concentrations of salt (which is why its also called salt water). This type of water is called hypertonic. Pure water has zero salt or any other dissolved solutes. It would be hypotonic. Tonicity refers to how much dissolved solutes something has.
The eye and cornea (and body in general) have a particular tonicity. This is why when you give fluids to someone, you have to give something called saline. Unlike hypotonic water, saline matches the tonicity of the body.
When water comes into contact with the eye, it will have a lower tonicity that the cornea. This will cause the water to absorb into the cornea to try to equalize the different concentrations. This causes swelling of the cornea.
In short, swimming in pool water, especially pool water with a low tonicity (or low concentration of dissolved things in it) will lead to swelling of the cornea. This will cause hazy blurred vision and halos around lights.
Treating Irritated Eyes After Swimming
So what can you do after the fact to help your burning eyes heal up? Well nothing is going to make it instantly go away, the epithelium has to heal over with time.
But there is a thing you can do to help promote the best environment for the eye to heal. If the eye continues to dry out, it will take longer to heal. Thus using artificial tears can prevent the epithelium from drying out and promote fast healing. These drops can also make the eye feel a little more comfortable in the meantime.
But ideally, it is best to prevent this eye irritation in the first place. The most effective way this is done is by wearing a good pair of swim goggles.
Summary
Chemicals used in the pool such as chlorine and its byproducts and the pH and tonicity can cause you to have extra eye irritation, burning, redness and blurry hazy vision after swimming. While this has to resolve on its own, using artificial tears can help get your eyes feeling more comfortable quicker.
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