What Is a Cornea?
Your cornea is the clear part of the eye that covers the colored portion of the eye. It is responsible for focusing light into the eye, which allows you to see clearly. If you're nearsighted or farsighted, you may wear contact lenses to refocus the eye. The contact lens, which is made of a thin, plastic material, sits over the cornea.
A cornea does not have blood vessels, which allows it to appear transparent. Because there are no blood vessels in the cornea, it relies on oxygen from the air to keep the eye healthy. When oxygen reaches the cornea, it dissolves in the tears, then carbon dioxide is emitted from the cornea.
Cornea Affects Oxygen
Placing a contact over the eye slows down the process of getting oxygen to the eye. While normal daily wear of contacts--wearing the contacts throughout the day, then removing them at night and while asleep--allows enough oxygen to reach the cornea, wearing contacts beyond that can begin to decrease the amount of oxygen that reaches the cornea.
When the cornea does not get enough oxygen, blood vessels begin to grow on and around the eye as the body's way of attempting to compensate for lost oxygen. Blood vessels can actually grow in front of the eye, which can result in a number of complications. These complications include eye infections, eyelid changes, allergies, warping of the cornea, eye swelling and in the worst-case scenario, blindness.
Further Effects
In addition to oxygen concerns, it is possible for the contacts to trap harmful bacteria underneath the lens, which is in contact with the cornea. If you regularly remove your contacts every night, clean them with a sterile contact lens solution.
Signs of contact lens irritation due to overwear include redness, blurry vision, sensitivity to light and pain. If any of these occur, you should remove your contact lenses and store them in contact lens solution.
