Age-related far-sightedness (presbyopia)

What is age-related far-sightedness?

Age-related far-sightedness (medical term: presbyopia) is due to the normal ageing process of the eye lens. If it sets in, the eye will no longer be able to focus as well at close range. For this reason, presbyopia is not a disease in the strict sense of the word, nor is it typical far-sightedness, because the cause is precisely this natural ageing process of the lens, which is also physiological (in contrast to pathological, i.e. disease-related).

It is interesting to note that the physiological changes of the lens start on the day of birth. The lens regularly adjusts the eye’s refractive power so that objects can be perceived equally at different distances: if the lens curves more, the refractive power increases so that nearby objects can be clearly projected on the retina. In the flattened state, however, the refractive power of the lens is lower, allowing distant objects to be clearly perceived. In medicine, this adjustment of visual acuity by a change in the shape of the lens is subsumed under the term ‘accommodation’.

Fortunately, the visual problems associated with age-related far-sightedness can be corrected by wearing glasses or contact lenses or by means of an operation or laser eye surgery.

Causes

The elasticity of the lens continuously decreases with age. Its rigid nucleus becomes larger, while the soft outer cortex becomes smaller. As a result, the accommodation capacity (accommodation = the eye’s ability to adapt flexibly to different distances) decreases.

In order to be able to see clearly at close range, the eye lens must be more spherical. Here’s how it works:

1. A particular muscle of the eye, known as the ciliary muscle, contracts.
2. This relaxes the suspension fibres of the lens and makes the lens more spherical.

In the course of life, however, the lens of the eye ages and can no longer change shape sufficiently; this is because it becomes thicker and harder over the years due to the thickening and hardening of the tissue. At birth, however, the eye lens is still very elastic.

Reduced range of accommodation

In general, presbyopia first becomes apparent around the age of 40 to 45 when the eye’s range of accommodation falls below three dioptres.

The term ‘range of accommodation’ refers to the visual area in which the eye can perceive objects in sharp focus. The lower limit is marked by the near point – the shortest distance at which someone can still perceive something sharply. The upper limit of the range of accommodation, on the other hand, is the far point, where clear vision is still possible. As we get older, the near point moves ever further into the distance – the range of accommodation decreases. For 10-year-olds, for example, it is still 15 dioptres, while for 30-year-olds it is 7 dioptres, and for 60-year-olds only 1 dioptre.

Treatments

The natural lens hardening process occurs sooner or later in all people and cannot be stopped by special eye training. Whether and when you start wearing glasses also has no influence on the process.

As with pathological far-sightedness, it is possible to compensate for the lack of refractive power of the eye lens in the case of age-related far-sightedness with glasses or contact lenses.

In treating presbyopia, a specialist distinguishes between the following methods:

Reading glasses: Reading glasses for people with age-related far-sightedness have positive lenses (i.e. there is a plus sign before the dioptre value), which are made of converging lenses. These curve outwards (Latin: convex) and focus the incoming light rays before they reach the eye. The strength of the glasses is adjusted depending on the degree of presbyopia. A pair of reading glasses makes clear vision in the near-distance possible again.

Bifocal glasses: Bifocal glasses avoid the annoyance of changing glasses for near- and far-distances. These glasses are designed to enable far-distance vision in the upper area of the lens and near-distance vision in the lower area.

Varifocal glasses: In the case of varifocal glasses, the lens is polished so as to allow the two areas for far- and near-distance vision to gradually merge into one another. They enable people with age-related far-sightedness to not only see clearly at a distance and close by, but also in the middle distance – for example, when working at a computer screen. However, varifocal glasses are not equally suitable for all patients or they often require a certain acclimatisation period, as wearing varifocal glasses can cause mild dizziness and headaches.

Computer glasses: People who spend a lot of time working at a computer may consider buying what are known as computer glasses (also known as workstation glasses or VDU glasses). They include several different zones that are tailored as closely as possible to your daily work.

Contact lenses: Age-related far-sightedness can also be compensated for with – soft or hard – contact lenses. It is particularly important that the eyes have been accurately measured beforehand by an ophthalmologist to ensure that the lenses fit correctly. The diameter and the radius of curvature are just as important as the plastic from which the contact lenses are made. Contact lenses should never be worn for longer than recommended, as the cornea needs a few hours during the day to be supplied with the oxygen it needs.

Surgical treatment

By implanting an artificial lens in the eye – or using laser technology, it is possible to counteract age-related far-sightedness.