I hear it all the time.
“Dr. Ross, why should I replace my contacts regularly?”
“They feel fine.”
“I just replace them when they start to bug me.”
“I know I should replace them every month but sometimes I just leave them in for a few months and I haven’t had a problem.”
“You guys always tell me to replace my contacts every month. It’s a scam, isn’t it? You just want my money!”
These are the words and actions of people who wear contacts that make eye doctors everywhere want to go and wash their eyes. So let’s go over WHY it is so important that you use and replace your contact lenses as directed.
I want you to imagine a tuna sandwich. Stay with me on this, I know that sounds a bit strange. Now, take that tuna sandwich and wrap it up in some saran wrap. When you do decide to eat your sandwich, instead of throwing away the saran wrap, imagine that you wash it off instead and keep it to use another day. The next day you make yourself a peanut butter sandwich. Now you have thoroughly cleaned that saran wrap so you use it again. When you finally get around to eating your peanut butter sandwich later that day it doesn’t taste quite right. In fact, it’s sort of like eating a tuna and peanut butter sandwich. If you keep reusing that saran wrap every day for a month you're going to have a whole variety of weird flavours and that last sandwich is going to be pretty gross.
Saran wrap is a plastic. It has pores in it to allow your food to breathe even while it is wrapped up. Those pores can get clogged with material, like tuna, and no matter how well you clean it those pores never fully open again. That means that not only does any other sandwich take on a distinctly tuna-fishy taste but also that the saran wrap doesn’t ‘breath’ as well as it did before.
You may have already guessed where I’m going here. Contact lenses are also plastic. They also have pores in them so your eyes can breathe. While you don’t have tuna in your eye, I hope, you do have protein, lipids (fatty molecules), dust, dirt, debris, and bacteria. These things all can and do clog the pores of your contact lenses which decreases how much oxygen gets to your eyes over time. Contacts need to be replaced at different times depending on their material which is why some contacts you use for a day, others for two weeks and others still for a month. Large amounts of research and testing goes into determining how long a contact lens is safe for you to use.
So now I’ve probably convinced you that contacts can be pretty gross if they’re not used properly. But what actually happens if you don’t get enough oxygen to your eye? What happens if you keep sticking a dirty, clogged up lens in there? The big, bad, scary thing that can happen, what no optometrist wants to see, is a bacterial ulcer. These things are nasty. They almost always happen right in the middle of your eye, hurt enough that you may seriously consider scooping out your eye, and they leave a really nasty scar. The result of that scar is loss of vision. The world doesn’t go black (you can still see some things) but don’t expect to see 20/20 again.
If you want to read more about contact lens safety check out this great website from the AOA.