An eye is farsighted if it has the visual defect of no longer being able to focus on nearby objects and thus to recognize them clearly. Farsightedness is a visual defect that is often caused by the fact that the eyeball is too short, so that the sharp image is only formed behind the retina. Another possible cause is a lens that is too weakly curved.
Long-sightedness correction
Correction is done with plus lenses, whose special refraction brings the image to the retina so that it can be seen and recognized in sharp focus.
Symptoms of farsightedness
Typical symptoms of an existing farsightedness are headaches and cramped eye muscles, which leads to “tired eyes”. The occurrence of the headaches and tension is often in the evening or after long work. In adulthood, it is not uncommon for mild farsightedness to go unnoticed until about 40 years of age, as the eye compensates for the visual defect by adjusting. However, if farsightedness occurs in children at an early age, it must be corrected quickly to prevent the maldevelopment of the eyes and brain region. Often a so-called astigmatism (astigmatism, astigmatism of the cornea) occurs parallel to farsightedness in children.
Therapy/correction of farsightedness
The lenses used for farsightedness are “plus lenses”, which means that their values are in the plus range. Spectacle lenses used for myopia, on the other hand, are in the minus range. The lens for the farsighted eye is converging/convex-ground, so that it is thicker in the middle than at the edges. This special cut brings the image forward so that it can be focused on the retina instead of being bundled behind the retina as in the uncorrected eye.
Long-sightedness levels
There are three different levels of farsightedness. In addition to the slight farsightedness of 0 to 2 diopters, which normally goes unnoticed until the age of about 40, there is the medium farsightedness of 2 to 6 diopters and the severe farsightedness of over 6 up to about 20 diopters. “Dioptre” here is the unit of refraction value and is necessary for determining the extent of the visual defect and the strength of the corrective lens.
The more pronounced the farsightedness is, the thicker the necessary glass in the middle and the heavier they are. However, there are now a large number of special lenses and cuts available on the market that allow a rather thin material to be used in spite of high visual impairment. The values for long-sightedness-correcting lenses can be found, for example, in the spectacle passport.