Farsightedness: Description
People who cannot see close objects sharply are considered to be farsighted. In most cases, this is due to an eyeball that is too short. Doctors then speak of axial hyperopia. Much rarer is the so-called refractive hyperopia: In this case, the farsightedness is due to an insufficient refractive power of the eye, i.e. the ability of the eye to focus incoming light rays is insufficient.
About 20 percent of all people under 30 are farsighted. In most of those affected, the refractive power of the eyes is below +4 to +5 diopters (dpt). Only a few people have higher readings and thus even more pronounced farsightedness.
Sharp vision near and far
Accommodation is made possible by a variable shape of the eye lens. This lens (in addition to the cornea) is responsible for the refraction of light in the eye. The eye lens is suspended by fibers from the so-called ciliary muscles:
- When the muscles tense, the lens curves more (becomes rounder) and its refractive power increases. This allows close objects to be seen sharply on the retina.
Convergence reaction
In order to see an object that is centered and close in front of our eyes, the so-called convergence reaction takes place. In this process, the two eyeballs move towards each other, the pupils constrict, and the refractive power increases due to a stronger curvature of the lens. Accordingly, accommodation and the convergence reaction are coupled.
Farsightedness: Symptoms
- rapid fatigability of the eyes
- eye pain
- burning eyes
- conjunctivitis (inflammation of the conjunctiva)
These symptoms are also summarized under the term asthenopic complaints. They become more noticeable mainly during reading.
Since anatomically the increase of the refractive power and the convergence of the eyes (convergence reaction) are coupled to each other, inward squinting is another possible symptom of farsightedness.
The reason for farsightedness can be either a too short eyeball (axial hyperopia) or a reduced refractive power of the lens (refractive hyperopia).
Axis farsightedness (axis hyperopia)
Although an affected person can see sharply in the distance, the lens of the eye must be accommodated even in this case, because its refractive power in the relaxed state is not sufficient even for distant objects. Therefore, the ciliary muscles, which cause a curvature of the lens and thus an increase in the refractive power, are constantly tense.
Refractive hyperopia (refractive farsightedness).
In refractive hyperopia, the eyeball is of normal length, but the refractive power of the lens is lower than normal. The consequences are the same as in axial hyperopia.
Farsightedness in older age
To learn how farsightedness develops in older age, read the article Presbyopia.
Farsightedness: examinations and diagnosis
- How long have you been experiencing discomfort?
- Do you have difficulty reading?
- Do you suffer from headaches?
- Do you wear glasses?
The doctor will then examine your eyes. To clarify possible farsightedness, the refractive power of the eyes can be measured – with the help of infrared light or a laser beam. Beforehand, you will be given eye drops that dilate the pupils.
Eye tests allow you to make a statement about the visual acuity of your eyes. To do this, you have to recognize different letters, numbers or shapes that are presented to you at a certain distance. In the process, the various characters become smaller from line to line. According to the line that you can still recognize perfectly, your visual performance is then assessed in relation to the distance.
Farsightedness: Treatment
Farsightedness can be corrected with a visual aid – glasses or contact lenses. So-called plus lenses are used (also called converging lenses). They are curved outward (convex). As a result, they focus the incident light rays even before they fall on the cornea. Due to this supporting refraction of the light, the relatively weak refractive power of the eye is sufficient to form a sharp image on the retina.
Laser treatment
Laser treatment for farsightedness can, in rare cases, leave a scar on the cornea. Then vision is no longer possible, and a corneal transplant becomes necessary.
Farsightedness: Treatment for aphakia
Sometimes the reason for farsightedness is a lack of lens (aphakia), for example after surgical removal of the eye lens in cataract. Then a converging lens of +12 dpt can be used as a visual aid or a new lens can be surgically inserted into the eye.
Unlike nearsightedness, which often increases over time, farsightedness rarely changes in severity over the course of a lifetime.
