Farsightedness - Genetics Home Reference - NIH

Farsightedness - Genetics Home Reference - NIH



Farsightedness

Farsightedness, also known as hyperopia, is an eye condition that causes blurry near vision. People who are farsighted have more trouble seeing things that are close up (such as when reading or using a computer) than things that are far away (such as when driving).

For normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. Some people who are farsighted have eyeballs that are too short from front to back. Others have a cornea or lens that is abnormally shaped. These changes cause light entering the eye to be focused too far back, behind the retina instead of on its surface. It is this difference that causes nearby objects to appear blurry. In a person with this condition, one eye may be more farsighted than the other.

If it is not treated with corrective lenses or surgery, farsightedness can lead to eye strain, excess tearing, squinting, frequent blinking, headaches, difficulty reading, and problems with hand-eye coordination. However, some children with the eye changes characteristic of farsightedness do not notice any blurring of their vision or related signs and symptoms early in life. Other parts of the visual system are able to compensate, at least temporarily, for the changes that would otherwise cause light to be focused in the wrong place.

Most infants are born with a mild degree of farsightedness, which goes away on its own as the eyes grow. In some children, farsightedness persists or is more severe. Children with a severe degree of farsightedness, described as high hyperopia, are at an increased risk of developing other eye conditions, particularly "lazy eye" (amblyopia) and eyes that do not look in the same direction (strabismus). These conditions can cause significant visual impairment.

In general, older adults also have difficulty seeing things close up; this condition is known as presbyopia. Presbyopia develops as the lens of the eye becomes thicker and less flexible with age and the muscles surrounding the lens weaken. Although it is sometimes described as "farsightedness," presbyopia is caused by a different mechanism than hyperopia and is considered a separate condition.