Hyperopia

Hyperopia is the refractive condition where the nearest point of focus is located at a point away from the observer. When one is farsighted, near objects may appear blurred as effort must be made to bring even distance objects into clear focus. The are a number of explanations for this optical condition. The eyeball may be too short, causing the image to be focused virtually past or behind the retina at the back of the eye. Or, the focusing lenses of the eye are too weak.

The primary focusing lens is the cornea, the clear window at the very front of your eye. The internal lens, called the crystalline lens, in an adjustable lens that alters your focus from distance to near. Sometimes, one of these two lenses may have a radius of curvature that is too flat. Although the eye is deficient in focal power, it can sometimes correct for this situation by requiring the internal crystalline lens to add the additional needed power. In small amounts of hyperopia, the eye can compensate for the refractive error, sometimes quite effectively and other times resulting in eyestrain or headaches. As the level of hyperopia increases, the ability of the vision system to deal with it declines and near objects can not be brought into clear or comfortable focus. At higher levels, even distance vision declines.

A factor further complicating the situation is the aging of the human eye. Beginning around age 25 and symptomatic by age 40 , the normal ability of the crystalline lens to add focal power decreases. The compensatory mechanism fails and even small amount s of hyperopia result in blurred near vision, and later blurred distance vision.

People often confuse this with presbyopia, the condition where the crystalline lens loss of focal power causes a need for near vision correction. You may hear "you get farsighted as you get older, so if you're nearsighted, your vision gets better ." This is not the case. If you start out myopic, you remain nearsighted and add the need for near vision aids as well. If you start out hyperopic, you need help with near vision sooner, and ultimately require vision correction for distance.

High levels of hyperopia pose a special concern. The neurological-motor function feedback system which tells the crystalline lens to add focal power also tells the muscles that turn the eyes in and out to turn inwards. The brain functions as an "if/ then" computer and assumes that for a given focal effort, the eyes should be aimed at a given point in space ahead of the viewer. Excessive focusing yields excessive convergence (turning in) of the eyes, resulting in eye strain, headaches, double vision, and general discomfort.

 In children, this could result in crossed eyes (accommodative esotropia), loss of depth perception, difficulty reading and problems concentrating on near vision tasks. The child sees perfectly at distance but not at near. In adults, the person just can 9;t see well and seeks near vision correction.

Finally, hyperopia may be combined with other optical corrections, including astigmatism and presbyopia. You can learn more by reading those articles.