Refractive errors are the most common cause of poor vision and a need for vision correction. Nearsightedness, farsightedness and astigmatism are all types of refractive errors. Astigmatism is an uneven curvature of the cornea and lens of the eye, which results in poor vision. Nearsightedness (myopia) and farsightedness (hyperopia) are also related to the shape of the eye. How nearsightedness and farsightedness affect one’s vision can be easily confused.
What is nearsightedness?
Nearsightedness occurs when an eye is too long and light rays are focused incorrectly. Normally, light focuses directly on the retina, but with nearsightedness, light rays are bent into a point of focus that is in front of the retina. The nearsighted eyeball is shaped more like an oval and is less round. As a result, an individual will be able to see clearly up close, but will strain to see and read at a distance.
Most often, nearsightedness is caused by a natural change in the shape of the eyeball, and is not the result of an eye disease. In rare cases, nearsightedness may occur because of another eye condition or disease. It is often an inherited condition and usually starts in childhood, stabilizing in late teens or early twenties.
Symptoms of nearsightedness include blurred vision when looking at distant objects, difficulty seeing images on a chalkboard, movie screen or television. Vision problems caused by nearsightedness may result in poor school, sports or work performance.
What is farsightedness?
The farsighted eye is too short, causing near vision to be blurry, whereas one would see objects in the distance more clearly. In a hyperopic (farsighted) eye, light is not focused by the time it reaches the retina. As a result, an individual will be able to see clearly at a distance, but will strain to see and read up close. Difficulty focusing can also be a problem associated with farsightedness.
Farsightedness can be corrected as the eye develops during childhood. As we age into adults, however, the eyes lose their ability to change the shape of the lens to focus on near objects. For this reason, many people over age forty notice farsightedness, which is more apparent with presbyopia (age-related decline in vision).
Farsightedness often runs in families, though it can also be the result of other eye conditions such as retinopathy, eye tumors and lens dislocation. Symptoms of farsightedness include blurred vision, difficulty seeing objects up close, aching eyes, eyestrain and headaches. Children may not experience symptoms, however, parents may notice their child rubbing his or her eyes, a complaint of headaches and general disinterest in reading. Farsightedness can also increase risk of a child developing crossed eyes.
Treatment for refractive errors
Refractive errors can be diagnosed with a normal eye exam. Both nearsightedness and farsightedness can be treated with contact lenses or eyeglasses. In this case, artificial lenses are shaped to the necessary degree to compensate for refractive errors. LASIK surgery can also correct refractive errors by changing the shape of the cornea so that they eye will properly refract light into a point of focus on the retina.
If you have difficulty seeing up close or at a distance, or notice a family member complaining of headaches, schedule an appointment with your eye doctor for an eye exam immediately.