Refractive errors include myopia, hyperopia, presbyopia, and astigmatism, eye conditions that are very common. Most people have one or more of them. Refractive errors can usually be corrected with eyeglasses or contact lens.

What is myopia (nearsightedness)?

If you have myopia you can clearly see close objects, but distant objects are blurry. Myopia is caused by the eyeball being too long. Myopia occurs in different degrees from minimal to extreme. The more myopic you are the blurrier your vision is at a distance and objects will have to be closer to you so you can see them clearly.

What is hyperopia (farsightedness)?

If you have hyperopia, you can see distant objects clearly, but close ones are blurry. Hyperopia occurs when the eyeball is too short for the light rays to focus clearly on the retina.

What is astigmatism?

If you have an astigmatism, the surface of the eye (cornea) is not perfectly round, rather it is more oval and doesn’t allow the eye to focus clearly. The cornea is very important in helping the eye focus light rays on the retina. Astigmatism rarely occurs alone. It is usually accompanies myopia or hyperopia.

What is presbyopia?

If you have presbyopia, you have the loss of the ability to focus up close that occurs as you age. Most people are between 40 and 50 years when they realize for the first time that they can’t read objects close to them. The letters of the phonebook are “too small” or you have to hold the newspaper farther away from your eye to see it clearly. At the same time your ability to focus on objects that are far way remains normal.

Courtesy: National Eye Institute, National Institutes of Health