In order for the eye to see, light rays must be focused on the retina, the layer of light sensitive cells lining the back of the eye. A refractive error means that due to its shape, your eyes don’t refract light properly, so the image you see is blurred. There are four basic types of refractive errors: Myopia, Hyperopia, Astigmatism, and Presbyopia.
How the Eye Works
A myopic eye is usually longer than usual or has a cornea that is too steep. As a result, light rays are focused in front of the retina. Close objects look clear but distant objects look blurred.
A hyperopic eye is shorter than normal or has a cornea that is too flat. As a result, light rays are focused behind the retina instead of on it. Most children are hyperopic and many don’t require glasses since their eyes are strong enough to compensate and focus the light rays on the retina. As we get older, we slowly loose our ability to focus and adults with hyperopia may have difficulty to see objects up close.
An eye with astigmatism has a cornea that is shaped like a football. Normally the cornea is round like a basketball. A round cornea is able to focus light rays evenly on the retina. With astigmatism, some light rays are focused properly and some light rays are not. This distorts or blurs the vision.
When you’re young, the lens in your eye is soft and flexible. Muscles in your eye can easily change its shape to focus on close objects. Around the age of 45, the lens has hardened and become less flexible. The muscles in the eye can’t change the shape of the lens and it becomes more difficult to read up close. You can have presbyopia in combination with myopia, hyperopia, or astigmatism. Eyeglasses and contact lenses are the most common ways of correcting refractive errors. These work by refocusing the light rays on the retina, compensating for the shape of your eye.
Refractive errors can also be corrected with surgery. Laser in situ keratomileusis (LASIK) is the most common way of surgically correcting most types of refractive errors. With LASIK, a small flap is med in the cornea and the laser is used to reshape the cornea. The flap is then repositioned and the eye is allowed to heal.
If you have blurry vision or want to talk with someone about refractive surgery, call to schedule an appointment with one of our doctors.