64 percent of Germans wear glasses. The reason seems clear only at first glance - ametropia. But which type of refractive error the glasses have to correct varies from person to person. Anyone who has always wanted to know exactly what short-sightedness, hyperopia, presbyopia and astigmatism mean, can find the answers here.
Myopia and hyperopia
Myopia (myopia) is one of the most common types of ametropia. Reliable estimates suggest that about one quarter to one third of the total population in Europe is short-sighted - more or less strong. While some barely notice their short-sightedness, perhaps need glasses for driving at most, others suffer a lot from them and can not go carefree through the day without correction.
All myopia can see close-up objects perfectly sharp - but only vaguely removed. This is due to the not very exact "construction" of the myopic eye. This is either a little too long - therefore, the lens already focuses the incident light rays before it falls on the retina in the fundus. Or the eye lens has too strong a refractive power. The result: The image striking the retina is slightly out of focus. The opposite of myopia is the
Farsightedness (hyperopia). The farsighted eye looks good at the distance, but has problems nearby, typically when reading. There are two reasons for this: Either the eye is a little too short. The lens does not focus the light exactly on the retina, but a little later. Or the refractive power of the lens is too weak. The image information incident on the retina is out of focus. By the way, at a young age the eye can compensate for a slight farsightedness due to a stronger curvature of the lens. Later, the lens loses this flexibility. Around 35 percent of Germans are far-sighted.
Presbyopia sooner or later becomes noticeable in everyone. At some point, the arms are too short for the daily newspaper reading, a reading glasses must ago. This is due to the decreasing lens elasticity. The focus on proximity does not work as well as it did at a young age. Most people therefore require glasses between the ages of 40 and 50, at least in some situations. Incidentally, this should not be bought at the petrol station or drugstore, but in specialist shops, in conjunction with an examination of the eyes and a detailed consultation.
The reason: Eyesight eyesight should be examined regularly by a specialist, as the degree of presbyopia changes. In addition, declining vision in old age may have other causes than just presbyopia; a regular examination is therefore urgently advisable. The standard ready-made goggles correct only the diopter, a cylinder misalignment or a different vision correction for the left and the right eye do not afford these glasses. Only one of the two eyes can see nearly as well with ready-made reading glasses - if at all.
Another inaccuracy of the eye may be an uneven corneal curvature. The expert speaks of astigmatism. The eye does not see a point as a point because of the uneven distortion of the cornea but as a rod. The brain corrects this, but the picture is still unclear. All the vision problems mentioned so far can be corrected with glasses or with a contact lens, depending on the degree of ametropia.