Earlier this month, Heidi Mitchell of the Wall Street Journal (WSJ) interviewed Optometrist Glenda Secor, chairwoman of the American Optometric Association's contact lens and cornea section. Based on that interview, Ms. Mitchell published an article entitled “Does Chlorine Affect Your Eyes?” Great topic. But the article didn’t really discuss chlorine’s effect on vision. Below are some thoughts on how the swimming and ophthalmology communities could approach this topic from a chemical standpoint. In particular, one should expect that chlorine in pool water reacts with the proteins in the eye to chlorinate those proteins. For me, this raises two questions: Is that bad? Can we make it better?
In concluding that swimmers should wear goggles, the article focuses primarily on the “bugs,” i.e., bacteria that live in pool water despite chlorination. Dr. Secor, the WSJ's eye expert, points out that eyes are “vulnerable to bacteria lingering in chlorine-treated water, since some contaminants aren't killed by the trace levels of chlorine often used in pools.” The article doesn’t provide any information about whether chlorine affects swimmers' eyes.
The eye doctor interviewed does not appear to understand the swimming community. According to the article, she “lives near a beach but doesn't swim in the ocean" because “salt water also is ‘pretty full of contaminants.’” Thankfully, Dr. Secor points out that "there has never been documented evidence that continuous exposure to the diluted chemical can cause permanent harm to the eyes." But she does not discuss any of the findings in this area or explore reasons support her conclusions. It might help for a swimmer-ophthalmologist to pick up this question. If you have any ideas, please add to the comments section below.
Although the article really doesn’t have anything to do with how chlorine affects a swimmer’s eyes, the topic is worth discussing. Here are a few points from the article that might serve as starting points for conversation:
The “tear film” appears to include “tear proteins,” which serve as a barrier layer over the eye. According to wikipedia, “the tear film coating the eye, known as the precorneal film, has three distinct layers, from the most outer surface. These three layers are (1) the lipid layer, (2) the aqueous layer, and (3) the mucous layer.
The lipid layer is made of oils. The aqueous layer includes water and proteins. The mucous layer also consists of proteins. From a chemical perspective, the eye is coated in water, lipids, and proteins.
We know that protein molecules react with pool chlorine. Accordingly, we should expect pool chlorine to react with a swimmer’s “tear film” by chlorinating it. This effect is akin to chlorine reacting with the proteins making up a swimmer’s hair and skin. In my mind this leaves two outstanding questions: (1) Does chlorinating your eyeballs lead to any long-term damage? (2) Can we come up with a way to treat chlorine-irritated eyes?
I am not an eye doctor. But, I would suspect that pool chlorine’s effect on eyeballs is short lived. It would stand to reason that a swimmer’s chlorinated tear film gets replaced naturally (over time) with a new tear film. This would explain why a swimmer’s red eyes go away with time. It would be interesting to understand whether continuously chlorinating the tear film creates any long-term damage. As pointed out above, there is no evidence suggesting long-term harm. (At the same time the WSJ just ran and article about chlorine's effects on vision without answering the questions about chlorine). It would also seem worthwhile to devise a simple solution to chlorine-red eyes. Currently, the most popular solution for "getting the red out" is a vasoconstrictor, like Visine. But, these drug products treat the symptoms rather than addressing the underlying cause (chlorine in the eyes). Potentially, there could be some value getting the chlorine out of swimmers' eyes rather than just getting the red out.
Based on chemical reasoning, chlorinated eye proteins should behave similarly to chlorinated hair and skin. In this case, treating the chlorinated eyes with an antioxidant solution would neutralize the lingering chlorine, thereby reducing the irritation. Here, I would probably start with an antioxidant solution designed to be gentle on the eyes. Most saline rinses are 0.9% salt water solutions. Potentially, one could swap an antioxidant salt (e.g., sodium ascorbate) for the sodium chloride, buffering the solution to physiological pH.
Despite failing to discuss chlorine’s reaction with eyes, the article concludes that swimmers should wear googles to protect their eyes from pool water. This seems like great advice because goggles would prevent exposing the eyes to the pool water. By preventing exposure to chlorine, that chlorine cannot react with the eyes. This is similar to wearing a swim cap to protect hair—by preventing chlorine exposure, a swimmer can prevent chlorinating the proteins making up biological fibers.