Eye Refraction Disorders

Refraction is the manner in which light from an object focuses through the eye and creates an image on the retina. This image is what you see when you look at something. However, sometimes the light is focused in such a way that the image is blurred. When this happens, you have an error of refraction. There are four that are most common. These are myopia, hypermetropia, astigmatism and presbyopia.

In myopia, nearby objects are easy for the person to see. But distant objects are blurry as they are focused in front of the retina. Myopia is also referred to as nearsightedness. Myopia is a very common eye problem that generally appears around age twelve. It appears to be genetic as it runs in families. It may continue to get worse until around age twenty but usually stabilizes at age 30 and does not worsen after that. Farsighted or hypermetropia focuses distant objects behind the retina instead of in front of the retina as happens with myopia. And again they may appear blurred. The eye has ciliary muscles that can contract and adjust the point of focus thereby producing a clear image. Farsightedness is generally present at birth. It also appears to be genetic and runs in families. Those who are farsighted may have no problem other than an ache or discomfort in the eye from constant use of the ciliary muscles. However, if the eyestrain is excessive or the ciliary muscles do not adjust enough, objects may appear blurry and glasses may be needed. For people who are farsighted, the ciliary muscles get weaker with age so they may need to increase the power of their glasses as they become older. When the eye is resting it is focused for distance vision. When the eye needs to focus on a closer object, the ciliary muscles thicken and contract the lens. This process is called accommodation. As people age, the lens hardens and is less able to contract and focus on nearer objects. The resulting condition is known as presbyopia. This usually happens to people around their mid forties. When this happens prescriptive lenses will be needed. Every few years up until age 65, the prescription will have to be stronger to accommodate the continued weakening of the ciliary muscles. The outside front part of the eye is called the cornea. Sometimes this part will have an uneven curvature. When this happens, vertical lines may be in focus but horizontal lines are out of focus. Or diagonal lines may be out of focus. Or horizontal lines are in focus and vertical lines are not. This condition is called astigmatism. It is present at birth and generally does not worsen with age. It is possible to have both astigmatism and another refractive error such as nearsightedness or farsightedness.

It is important for people to visit an ophthalmologist for an eye examination to be sure they do not have any problems with refraction. Parents should also see that their children have an eye examination. Poor eyesight can cause learning problems for school children and result in their falling behind academically.