Presbyopia (also presbyopia, presbyopia) results from aging of the eye lens. She is noticeable from the age of 45. As with the actual farsightedness, those affected have problems reading at normal reading distance. With appropriate glasses, this can be resolved. Learn all about presbyopia here.
What is presbyopia?
Presbyopia is not a disease in the true sense of the word, nor is it a typical hypermetropia. The reason for the presbyopia is an aging process. Since it is completely natural, it is also called physiological (as opposed to “pathological” = “disease-related”).
The physiological changes of the lens begin with the day of birth. To allow objects to be perceived equally well at different distances, the lens adjusts the eye’s power accordingly: As it bends more sharply, the refractive power increases and nearby objects can be sharply imaged on the retina. In the flattened state, the refractive power of the lens is lower – then distant objects can be perceived sharply. This adjustment of visual acuity by changing the lens shape is called accommodation.
Presbyopia: accommodation diminishes
With age, the elasticity of the lens decreases continuously. Their rigid core gets bigger as the soft bark gets smaller. Therefore the accommodation capacity decreases. Around the age of 45, presbyopia is first noticed, when the so-called accommodation width falls below three diopters (3 dpt):
The accommodation width specifies the viewing area in which an eye can perceive objects sharply. The lower limit is marked by the near point – the shortest distance in which someone can still perceive something sharply. The upper limit of the accommodation width is the far point, ie the farthest point at which sharp vision is still possible. With age, the near point moves further and further into the distance – the accommodation width decreases. For example, it is still 15 diopters for ten-year-olds, seven diopters for 30-year-olds, and only one diopter for 60-year-olds.
Above all, people with presbyopia suffer from the fact that reading becomes more exhausting. You have to hold a book or a newspaper farther and farther away in order to recognize the letters clearly. The reading distance is thus increased. Normally it is between 30 and 40 centimeters. With presbyopia, he keeps on growing until his arms are too short to keep the book or newspaper sufficiently far away.
Correction of presbyopia
As with pathological farsightedness, presbyopia also offers the possibility of compensating for the lack of refractive power with glasses or contact lenses. The reading glasses for age-visionary (as well as far-sighted) people have plus glasses, which consist of collecting lenses. They are bent outward (convex) and focus the incoming rays of light before they hit the eye. The spectacle thickness is adjusted to the degree of presbyopia.
If shortsighted people age over time, this must be taken into account when selecting the glasses: Who is only a little short-sighted, the glasses can now read to decrease from the onset of presbyopia. For more severe myopia, however, the person concerned needs either two different glasses or a pair of progressive lenses, which combines both glasses in one another, or multi-strength contact lenses.
If farsighted people are additionally age-prone, the diopters necessary for both refractive errors must be added together. Overall, the lack of sight is then relatively strong. The opposite is the case with short-sighted people: Here, short-sightedness and presbyopia can even cancel each other out at close range, so that they can do without reading glasses for a relatively long time.
The following types of spectacle lenses are available for the treatment of presbyopia:
- Bifocal glasses: These are ground in the lower part of a converging lens for the near correction. The upper and middle part of the lens is a lens for remote correction.
- Three-Star Glasses (Trifocal Glasses): Here, between the near and far part, a third lens is ground. This means that those affected see sharp even at medium distances, even if they have completely lost their accommodation ability.
- Progressive lenses (progressive lenses): With these, sufferers can see sharply without any image leaps at any distance. The edges of the picture, however, are heavily distorted.
Let presbyopia be lasered
As with pathological farsightedness, one can also have the eyes lasered at presbyopia. However, the procedure is at presbyopia is usually not successful and is therefore rarely performed.