Hypermetropia » What is hypermetropia (farsightedness or hyperopia)

Hyperopia (farsightedness, hypermetropia) is a refractive disorder, when light rays enter the eye, which is in accommodative composure. Light rays are refracted by an optical system and their focal point is created behind the retina. Due to this process, a fuzzy, blurred image of the observed object creates in the eye. This specific phenomenon can occur when reduced refraction of the eye optical system, particularly of cornea and lens in lesser extend (refractive hyperopia) and when the shortening of the aterodorsal lenght of the eye (axial hyperopia). In a large extend, hypermetropia depends on the lenght of the eye (axial hyperopia).

The focal point created behind the retina means that the hypermetropic eye compared with a normal-seeying eye is too short, not fully developed, shorter than physiological 24 mm.

In most cases, the lenght of the eye is reduced at most 2 mm. We know that a change of 1 mm in lenght of the eye causes a change of refraction by 3 diopters and therefore we seldom observe hyperopia with higher amounts than +6 diopters.

Therefore, farsighted people are forced to accommodate more than emmetropes or the short-sighted and have to do so when looking at all distances. They see poorly in the close and into the distance, which may not always be ideal. Mostly, it is significantly worse in the close and at lower amounts there is a possibility of sharp vision into the distance, but only to a certain age.

Hypermetropic eye has to increase refraction of its optical system during accommodation (sharpening into different distances). Increased contraction of the ciliary muscle contributes for that and the suspended aparatus of the lens releases and the lens extends its curvature. The lens flares outward, its vergency increases more than in the case of emmetropic or myopic eye and the entering rays are directed onto the retina.

A man without a recractive disorder has to increase accommodation by 3 diopters when working in the close in the distance of 33 cm, while a hypermetrope with the refracion of +2 diopters needs to have it increased by 5 diopters. At the low level of this refractive disorder, the eye can correct its blurred vision by its own increased accommodative effort and is able to see clearly enough, even without correction. This ability is only temporary and sooner or later losts with age.

Children are born with hyperopia. Essentially, everyone is a strong hypermetrope when born. Anterodorsal lenght of the eye is about 18 mm. Gradually, as an organism grows, the lenght of the eye also extends. It follows, that all eyes should become emmetropic with time. In fact, about 50% of eyes remain farsighted.