Refractive Errors

Nearsighted – Myopia

myopia_imageNearsightedness, or myopia, is the most common refractive condition and affects one in four people. Nearsightedness is a condition in which light rays entering the eye focus in front of the retina instead of directly on the retina. Nearsightedness is normally caused when the eye is too long or the cornea is too steep. Nearsighted patients see nearby objects clearly, but have difficulty focusing on distant objects. Myopia can be minimal, creating only slight blurring of distant vision. Those with minimal myopia may be able to read the doctor’s eye chart without glasses. Those with moderate myopia are barely able to see the big E on the eye chart without glasses or contacts. Nearsightedness is often inherited, usually starts in childhood and stabilizes in the late teens or early adulthood.

Farsighted – Hyperopia

hyperopia_imageFarsightedness, or hyperopia, is a condition where light rays entering the eye focus behind the retina, resulting in blurry vision. In a hyperopic eye, the light rays do not converge or focus by the time they reach the retina. Hyperopia results from having an eye that is shorter than normal or a cornea that is flatter than normal. In this condition far vision is better than near vision. If the amount of farsightedness is large enough, and depending on the age of the patient, it will also blur distant objects, however the near vision will still be worse.

Astigmatism

astigmatism_imageIf your vision is blurred at all distances, you may have astigmatism. This condition is the result of having a corneal surface that is irregular in shape, somewhat like a football instead of a more rounded basketball. With astigmatism, the rays of light do not converge into a single point but form two or more focal points. Thus the eye is unable to focus clearly at any distance because of this irregular focusing surface. This causes people to experience blurry or distorted vision.

Presbyopia

During childhood, our eyes have the ability to focus on objects as close as our nose to objects very far away. The lens in our eyes acts similar to focusing lens in a camera. As each year passes, that ability to “focus” decreases. Typically, by the time we reach our forties, we will need an aid, such as reading glasses or bifocals, to focus on objects near to us. This condition is called presbyopia.

When a nearsighted (Myopic) person is wearing glasses or contact lenses to correct their vision, they too experience presbyopia. Because the nearsighted eye has a natural focal point “at near”, many nearsighted presbyopes can remove their glasses or contact lenses and read or do close work comfortably. Many myopes choose to wear bifocals to eliminate the need for removing and replacing their glasses. If you plan to have refractive surgery to eliminate or reduce your myopia, like everyone else, you will still experience presbyopia sometime in your forties. Likewise, farsighted patients will also experience presbyopia and need reading glasses whether or not they have had LASIK.

Many presbyopic contact lens wearers choose to wear a contact lens on one eye that does not fully correct the myopia, enabling that eye to focus on objects at near, while the other eye focuses well on distant objects. This type of correction is called monovision. There are various types of astigmatism including regular, mixed, asymmetric and irregular astigmatism. Corneal topography will define astigmatism in the greatest detail. Patients who have astigmatism should feel comfortable that it is routinely corrected with their nearsightedness or farsightedness at the time of surgery.

If you have any questions or would like to schedule a free consultation with Southwest Eye Institute please call us at (702) 368-2010 or contact us online.

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