Contact Lens Overwear
Back in the 1500s Leonardo Da Vinci was the first to develop the concept of a contact lens. If Leo could only see us now he would marvel at the hundreds of contact lens designs and dozens of highly sophisticated plastic polymers. Today it’s rare that a patient cannot be fitted with some kind of contact lens.
But are we treating our eyes well?
It’s true that contact lenses are wonderful and they provide an excellent alternative to glasses. But contact lens use is not without risk and the potential for vision-threatening problems is present especially in those who abuse the use of contacts.
Contact lens complications: It’s mostly about oxygen!
First of all it’s important to understand that wearing contact lenses is very safe...assuming it is not abused. When you think of contact lens-related complications you must think in terms of oxygen. That’s right oxygen.
Simply stated even the best fitting contact lens causes a compromise of the oxygen supply to the cornea. When a contact lens is in the eye not as much atmospheric oxygen gets through to the cornea as compared to when there is no contact lens on the eye. Over a long period too little oxygen is not good.
What can happen?
If you were to continue using a disposable razor you’d eventually knick your skin by the dulled blade. Disposable razor blades are meant to be thrown away after a period of time. It’s similar with disposable contact lenses. They are meant to be discarded after a designated period of time.
It’s important to understand that overwearing your contact lenses whether it’s too many hours in a day or too many weeks before discarding may not cause you to experience any symptoms. Here lies the danger. If the cornea doesn’t receive enough oxygen it actually becomes somewhat anesthetized being less able to experience pain or discomfort. All eye doctors have seen patients with various degrees of contact lens-related corneal abrasions often without any symptoms.
Several things can happen when the cornea is deprived of enough oxygen. The term deprive does not mean completely cutting off the oxygen supply but instead refers to a subtle reduction in oxygen supply over a long period of time. Slow starvation if you will.
Abnormal blood vessel growth
In the normal eye the cornea is perfectly transparent tissue with no blood vessels. If the cornea is deprived of enough oxygen over a period of time blood vessels from the surrounding tissues can grow into the cornea. This is a response of the cornea “calling out” for oxygen; it’s the body’s natural reaction to send in blood vessels. The aim of these new blood vessels is to deliver fresh oxygen to the starved corneal tissue. If left untreated these vessels can continue to grow into the cornea and can interfere with vision. Incidentally these vessels are permanent. They remain even if one is to cease wearing contact lenses. So prevention of their growth is key.
Surface cell problems
Another adverse effect of reduced oxygen supply involves the single layer of cells on the surface of the cornea. These epithelial cells are very sensitive to reduced oxygen supply. Over time they can swell and become loosened from their firm attachment to the cornea leaving openings in the cornea’s protective surface. These openings in the surface are opportunities for bacteria to cause infection. If too many epithelial cells slough off an abrasion or worse a corneal ulcer can form.
Lastly we now know that reduced oxygen supply to the cornea causes various bacteria to be able to bind to the epithelial cells. Healthy well-oxygenated epithelial cells tend to resist bacterial binding. Obviously when bacteria bind to the surface cells they are in a position to cause an infection.
Preventable
All these complications are highly preventable through the use of common sense. Don’t wear your contact lenses all the time. It’s important to give your corneas a regular “oxygen break”. If you are just hanging around the house it’s a nice opportunity to give your eyes a rest by wearing your glasses. Avoid wearing your contacts for all your waking hours.
Disposing of your lenses
The reason to dispose of your contact lenses after a designated wearing period whether it s two weeks or one month once again has to do with oxygen. When a new lens is placed on the cornea the level of oxygen getting through to the cornea is at its peak. Over time as the lens is worn and becomes layered with tear proteins as well as other debris and makeup corneal oxygen levels begin to diminish. Unfortunately some patients continue to wear their lenses far beyond the safety point. Since they frequently have no symptoms they mistakenly believe that nothing is wrong. Don’t be deceived into this way of thinking. A fresh lens will give your corneas the oxygen they need.
The big picture
One must think in terms of the long haul when wearing contact lenses. It’s important to maintain optimal corneal health throughout life. You’re not doing yourself any favours by wearing lenses too many hours each day or wearing your lenses past their designated life span. Remember the key is to keep as much oxygen flowing to the cornea as possible.
Stay in close touch with your doctor
Your doctor will examine your corneas to make sure none of the problems we’ve talked about are taking place. Adhere to the lens replacement and appointment schedule you are given by your doctor. If you suspect that you do have a problem if your eye gets red or if your vision is blurred or painful stop wearing your contact lenses and call your doctor’s office.
Giving your eyes a reasonable oxygen break each day and replacing your lenses when you’re supposed to will help ensure that your corneas remain healthy and that you have many years of problem-free clear vision with your contact lenses.