Contact lenses sit on the surface of the eye over the cornea. The lenses can be made of a soft silicone material or a rigid material called gas permeable or hard, PMMA lenses. Both types of lens material, if worn improperly or for too long, can cause the cornea to change shape.
Understanding Why the Shape of The Cornea is Important for Contact Lens Wearers
The cornea is the thin, clear outer layer of the eye. Light passes through the cornea and through the crystalline lens of the eye and to the retina. Wearing contact lenses can sometimes change the shape of the eye. When this happens, many problems can occur within the eye, including oxygen deprivation, vascular problems, and even altered vision.
When a person first gets their contact lenses, the eye doctor measures the cornea with a tool called a keratometer. This machine measures the surface of the eye, and the doctor uses the measurements to prescribe a lens designed to fit the front surface of the eye. Proper fit is important for both good vision and good eye health.
How Contact Lens Wearers Can Avoid Reshaping the Cornea
To help reshape a warped cornea or avoid a cornea becoming damaged:
- Make sure the lenses are sitting on the eye properly. The best way to tell if the lens is correctly on the eye is to have the eye doctor or contact lens technician recheck the fit. This can be done quickly in a short appointment called a recheck. Lenses can tighten and loosen after wearing them for several weeks or months.
- Give the eyes a break. Wearing time, the length of time per day lenses are permitted to be worn, varies depending on the type of lens and individual, general eye health. An eye care professional determines the proper wearing time during the initial contact lens fitting. Wearing lenses too long can affect the cornea through lack of oxygen to the eye. Following the wearing schedule and wearing glasses occasionally gives the eyes a time to rest and breathe.
- Inspect contact lenses regularly for tears, cracks or rips. A lens can be damaged but not feel any different. Wearing damaged lenses can affect fit and cause corneal problems.
- Practice proper lens hygiene. Cleaning all types of contact lenses regularly helps avoid deposits that can accumulate on the surface of the contacts. If lenses are continued to be worn, there is a risk of potentially serious side effects including corneal damage.
- Follow a regular exam schedule. Contact lenses are a medical device and are regulated by law for patient protection with expiration dates. Wearing expired lenses can potentially cause many problems, including corneal fit.
Corneal Reshaping with Contacts Can Be Intentional
Recently, eye doctors have been using a technique to intentionally reshape the cornea through Orthokeratology (Ortho-K) or Corneal Refractive Therapy (CRT). This is done by wearing a special contact lens at night that gently reshapes the surface of the eye, but the results are temporary and must be repeated each night. This procedure is usually used on people who are nearsighted.
Contact lenses are one of the most common medical devices used today. They are convenient and fairly easy to use. Properly wearing the lenses and taking good care of them is key to avoiding problems such as corneal swelling or reshaping.