Contact Lenses

Why did I stop tolerating contact lenses?

The longer a contact lens is left in your eye, the more likely your immune system is to classify that little piece of floating plastic as an intruder.

Joel Hunter, MD
Joel Hunter, MD
Refractive Surgeon, Hunter Vision Updated 07/09/17 7:10 PM

To clarify right here at the start, I’m really not anti-contacts. They are amazing considering the fact that modern technology has engineered a way for people to put a foreign object in their eye and leave it there for a long time, usually with no ill side effects. It’s insane that is possible. It’s why contact lenses so popular. But because they are so popular, those instances where things go awry are pretty well-known. If contacts have a 1 in 1000 chance of some problem, and millions upon millions of people are wearing them every day, then you’re going to see some contact lens problems. The sudden inability to tolerate contacts is one of those. Writing a bunch about contact lens intolerance can make someone sound like they hate contacts. But I don’t. This is about when someone’s eyes hate contacts, and that’s different.

The reason contacts can suddenly become impossibly irritating after years of easy wear is because of how eyes function. Eyes have somewhat of a “fool me once, shame on you; fool me 5,000 times, shame on me” policy. The number of times they can be fooled equals the number of days a foreign body was allowed to sit in contact with the front of the eye and go relatively undetected. Each day, or week, a contact is left sitting there, increases the likelihood an eye will wake up and realize what’s going on. There are two main reasons for your eye to become more biased against contacts over time. They are what lead to that tipping point where contacts suddenly become impossible to wear.

The first reason has to do with how your body’s immune system operates in general. You’ve got roaming white blood cells always on patrol looking for anything that doesn’t have permission to be in your body. When an offender is found, biochemical sirens go off and it’s a full-scale assault to destroy the invader. A ton more white blood cells and/or inflammatory molecules arrive, and it becomes a microscopic war zone for a time. Here’s the cool part (except when it comes to contacts): new specialized white blood cells rise from the ranks after the attack. How are they special? They are the ones built to recognize that foreign invader specifically. And now there are tons of them. It won’t stand a chance next time, and that’s why it’s really rare to get the same cold twice. That strain of virus is on the no-fly list and gets booted out before it can ever get started.

For the second reason, it’s an eye-specific issue. Contacts rest on the front of the eye. While there is some cool hydroplaning between the contact and your tear film, it isn’t always floating at all points. The most common example of a pressure point is where a contact sits underneath the upper lid. In that spot, it is pressing on some easily-offended cells ringed around the cornea called limbal stem cells. They’re the stem cells that are constantly creating new cells for the topcoat of epithelium on your eye. When they die, tiny new blood vessels grow into the area and try to fix things up. It doesn’t work, but it does open up new highways for white blood cells to patrol.

Herein lies the problem. You’ve got a contact presenting the same foreign intruder all day, every day. It may be an environmental allergen or even some component of the contact itself, but it doesn’t matter. What matters is that it’s there. Just sitting there all the time, gloating as it defies your body’s strict “no foreign invaders” rule. It may do that for 10 years while dopey white blood cells—like some kind of microscopic, bumbling country sheriff—wander close by but never quite recognize the threat. Then eventually some new blood vessels show up around the edges of the cornea. They may be too small to see, but they’re big enough to bring several million patrol units through the area each day. By then, it’s just a matter of time.

Once the threat is recognized, it’s game over. Your immune system will step up production of countless, specialized fighters for that specific foreign body. White blood cells and little molecular “Wanted” posters called antibodies will make it impossible to get past your eyes’ security ever again. For you, it feels like you’ve developed a sudden inability to wear contacts. Your body doesn’t see it that way, though. It is a hard-fought victory against another enemy against the great nation-state of cells that comprise you. I don’t hate contacts. Your eyes though? Sometimes they do.

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