Contact Lenses: The Eyes Have It!
Over 40 million people in the U.S. wear contact lenses. When properly cared for, they can be a safe and effective form of vision correction. When used incorrectly, not only may your vision be affected, but also the health of your eyes.
Our eyes are divided into two sections, both are filled with fluid. The pressure from the fluid fills out the eyeball and helps to maintain its shape.
The outer covering of the eye is a tough, white layer called the sclera.
The cornea, a curved, clear membrane, is the covering for the colored part of your eye, and is the first layer that light rays hit. It protects your eye, and assists in focusing light rays onto the retina, which lays at the back of the eye.
Beneath the cornea is the pupil, the black dot in the center of your eye. This is a hole that light rays travel through. The iris is the colored part of your eye. It controls the amount of light that enters the eye by enlarging (dilating) or shrinking (constricting) the pupil. The iris allows more light into the eye when the environment is dark, and allows less light when the environment is bright.
Behind the iris is the lens. With the use of small muscles, the lens is able to change its shape to focus light onto the retina. The lens becomes thicker to focus on nearby objects, and thinner to focus on distant objects.
The retina converts light rays into impulses that travel via the optic nerve to the brain, where they are interpreted as the images we see.
Refraction is the ability of the cornea and lens to bend light rays directly onto the retina, creating a clear image.
Our eyes are equipped with built-in protections:
· Orbit: The bony sockets our eyes rest in
· Eyelashes and Eyelids: Mechanical barriers that keep foreign particles away from our eyes through involuntary blinking (such as when exposed to dust, insects, and bright lights)
· Conjunctiva: The moist surface lining the eyeball and eyelids that protects the sensitive tissues underneath
· Tears: Bathes the surface of the eye to keep it moist. They transfer oxygen and nutrients to the cornea, and sweep away small particles that enter the eye. Tears are also rich in antibodies that help prevent infection
Refractive errors occur when the cornea and lens can’t sharply focus the light rays onto the retina, resulting in blurred vision:
· Nearsightedness (myopia) means you can only see objects that are near. This occurs when the eyeball is too long for the cornea and lens to focus light rays onto the retina
· Farsightedness (hyperopia) means you can only see objects that are far away. This occurs when the eyeball is too short for the cornea and lens to focus light rays onto the retina
· Presbyopia (presbys: old; opia: eye): The lenses stiffen with age, making it more difficult for older adults to see both near and far images
· Astigmatism: This is when the cornea or lens is not perfectly round, which can cause objects to appear blurred at a distance
Contact lenses are medical devices and regulated by the FDA. They are placed directly onto the cornea. Contact lenses work by changing the way light enters the eye, so it can focus directly onto the retina. They (and glasses) require an eye exam to measure the curvature of your cornea and lens, and a prescription for the exact correction needed.
Contact lenses come in a variety of options: soft, hard, daily wear, extended wear, disposable, and bifocals (near and far vision correction).
Failing to wear, clean, and store your lenses as directed by your eye doctor raises the risk of developing serious eye infections.
· Wash your hands with soap and water, and dry them well before touching your contact lens
· Don’t sleep in your contact lenses unless prescribed by your eye doctor
· Keep water away from your contact lenses. Tap water can contain bacteria, leading to eye infection. It can cause soft contact lenses to change shape, swell, and stick to the eye. This can scratch the eye, leading to infection
· Rub and rinse your contact lenses with contact lens disinfecting solution, never water or saliva, to clean them each time you remove them
· Only wear your contact lenses for the prescribed amount time
· Replace your contact lenses as often as recommended by your eye doctor
· Don’t “top off” solution. Use only fresh contact lens disinfecting solution in your case. Never mix fresh solution with old or used solution
· Use only the contact lens solution recommended by your eye doctor
For more information, visit the CDC at https://www.cdc.gov/contactlenses/index.html