Age-related far-sightedness (presbyopia)
If you are over the age 40 to 45, you may be familiar with the following phenomenon:
you go to the library, pick out a book and a cosy corner to browse, and then try to read the book with your arms outstretched, but the script seems too small and the arms too short.
Unfortunately, in such cases, the font size or the length of your arms is rarely the reason why you are no longer able to decipher the letters properly; no, you are experiencing age-related far-sightedness.
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.
Symptoms
The first symptoms of age-related far-sightedness usually appear from the age of 40 onwards. As a result, reading at a normal reading distance becomes increasingly difficult. In addition, the image in front of the eyes may become blurred and a person may experience a dull feeling of pressure in the forehead or eyes.
Incidentally, the range up to which the eye can focus shifts further and further into the distance over the years – until it reaches around two metres by the age of 65.
Over time, close-up vision causes more and more problems: text and contours appear blurred, and those affected usually instinctively hold a book or price tag further away to enable them to continue reading letters and numbers.
For people who are not affected by age-related far-sightedness, the ‘normal’ reading distance is between 30 and 40 centimetres. In the case of presbyopia, however, the reading distance continues to increase until ‘the arms are too short’ to keep the book or the newspaper far enough away for reading.
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:
- A particular muscle of the eye, known as the ciliary muscle, contracts.
- 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.
Diagnosis
Anyone with visual problems should seek an ophthalmologist’s examination as soon as possible, if only to rule out other eye diseases. Various tests show the ophthalmologist whether the eyes require support:
Eye charts: The visual acuity of the eye can be easily determined using what are known as eye charts. The patient is asked to read out numbers or letters, which are projected onto the opposite wall in different sizes. Each eye is tested individually.
Test with phoropter: A phoropter is a device for measuring the subjective refraction (= measuring the refractive power of the lens) of the eye. The phoropter consists of two sets of lenses arranged one after the other, each of which sits in a frame and which are needed to compensate for what are known as refractive errors. If such a refractive error exists, it means that the light rays penetrating the eye are not focused on the retina and therefore cause a blurred vision.
When a test is carried out with a phoropter, the patient looks through a device and indicates which letters and numbers he or she can identify. Correction lenses of different thicknesses can be adjusted. An alternative to a phoropter are optometry glasses, which can also be fitted with lenses of different thicknesses. This allows the right lens to be determined for near and far vision.
Test with refractometer: With the aid of a refractometer, the refraction of light in the eye can be measured without the patient having to do anything. He or she simply sits in front of the refractometer and looks through an optical system. The device emits rays of light into the eye, which are focused by the cornea and the lens and ultimately hit the retina. The device then checks the refraction of light, which allows it to calculate which lens strength would be optimal to enable the patient can see clearly again at near and far distances.
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.
Aftercare
To ensure that the eyes are healthy and that the correct visual aid is being worn, it is advisable to visit an ophthalmologist on a regular basis. This is the only place where the eyes can be properly examined and, if necessary, the necessary tests can be carried out.
FAQs
What happens if someone who is already near-sighted becomes long-sighted?
If near-sighted people develop age-related far-sightedness over time, this must be taken into account when choosing the strength of their glasses: If someone is only slightly near-sighted, they can reduce the use of glasses for reading at the onset of age-related far-sightedness. Near-sightedness and age-related far-sightedness can even cancel each other out in the near-distance range. In the case of severe near-sightedness, on the other hand, the affected person needs either two different pairs of glasses or varifocal glasses, which combines both lenses, or multifocal contact lenses. Computer glasses are recommended for working on a computer.
What happens if someone who is already far-sighted develops age-related far-sightedness?
If far-sighted people also develop age-related far-sightedness, the dioptres necessary for far-sightedness and presbyopia must be added together. Overall, vision is then severely restricted because, when age-related far-sightedness sets in, far-sighted people will no longer be able to see clearly at near-distance and later also in the far-distance. This process is noticeable a little earlier than in people with normal vision – as early as between the ages of 35 and 45, in fact.
Why is presbyopia not considered a refractive error?
Age-related far-sightedness is neither a form of refractive error nor an eye disease, as the lens of the eye ages in everyone.
