All About Presbyopia

Which treatments help with presbyopia, from glasses to contact lenses to laser – and why the term “presbyopia” is wrong. A detailed look at presbyopia …

Background: Because the lens of the eye ages in all people, presbyopia is not an illness and is not a defective vision. To translate presbyopia with “presbyopia of old age” would therefore be wrong. This is because farsightedness is a refractive error of the eye.

What are the causes of presbyopia?

With presbyopia, the so-called accommodation no longer works properly. Accomodation describes the ability of the eye to adjust flexibly to different distances.

In order to be able to see sharply at close range, the lens of the eye must become more spherical. This is how it works:

• A certain eye muscle, the ciliary muscle, contracts.
• This relaxes the suspension ligaments of the lens.
• The lens becomes more spherical.

In the course of life the lens of the eye ages. At birth it is very elastic. Over the years it becomes thicker and harder as the tissue thickens. The consequence: the lens can no longer deform sufficiently.

The eye no longer bundles the incoming light rays from nearby objects correctly. The so-called refractive power of the lens decreases. Objects at close range are only blurred on the retina at the back of the eye. Thus, the eye is still normal-sighted at a distance because it can still image a distant object sharply on the retina. But near vision deteriorates.

While a two-year-old child can see sharply at a distance of five centimetres, a seven-year-old can focus at seven centimetres. At the age of 20, it only works at a distance of ten centimeters, at 40 it is already 25 centimeters, at 50 it is even 50 centimeters, at 65 the close-up only works at two meters – but at this age the changes in the eye are complete.

Does presbyopia also exist in short-sighted and far-sighted people?

Presbyopia and myopia

Nearsightedness is usually caused by an eyeball that is too long or by an error in the refraction of the incident light. As a result, the light rays are bundled too strongly, so that the focal point is not on the retina at the back of the eye, but in front of it. As a result, short-sighted people do not see clearly in the distance.

An additional presbyopia, which sets in from the age of 40, is not a problem for many short-sighted people, because myopia compensates for the resulting presbyopia.

Presbyopia and hyperopia

Long-sightedness is caused by a too short eyeball or an altered refraction of the cornea or lens. The consequence: the focal point of the incident light is not on the retina but behind it. In young people, the eye can largely compensate for this refractive error through the activity of the ciliary muscle in the eye, so that many people do not even notice that they are farsighted.

When presbyopia sets in, farsighted people can no longer see clearly, first at close range and later at a distance. The process becomes noticeable a little earlier than with normal vision – namely, between the ages of 35 and 45.

Symptoms of presbyopia

In most cases the symptoms of presbyopia first appear at the age of 40. At first they are most noticeable in dim light or fatigue.

The first signs may be:

• reading becomes strenuous
• the picture blurs
• there is a dull feeling of pressure in the forehead or in the eyes

In the course of time, seeing close up causes more and more problems, text and contours appear blurred. Affected people usually instinctively hold the book or the price tag further away to be able to read letters and numbers. At some point, the length of the arms is no longer sufficient. Reading is hardly possible any more.

How is presbyopia diagnosed?

Anyone who notices vision problems should have an ophthalmological examination – if only to rule out other eye diseases. Various tests show whether the eyes need support:

• Visual acuity charts: The visual acuity of the eye can be easily determined with the help of visual acuity charts. The patient is asked to read out numbers or letters, which are shown in black on a white background in different sizes. Each eye is tested individually.
• Test with phoropter: In order to be able to determine the best possible visual acuity for distance and closeness more precisely, a similar test follows. The person concerned looks through a device and indicates which letters and numbers he or she can recognise. Correction lenses of different strengths can be adjusted. An alternative to such a phoropter is measuring glasses, which can also be fitted with lenses of different strengths. In this way, the correct lens for distance and closeness can be determined.
• Test with refractometer: With the help of a refractometer the refraction of light in the eye can be measured without the patient having to do anything. He simply sits in front of the device and looks through an optical system. The refractometer sends light rays into the eye, which are bundled by the cornea and the lens and finally hit the retina. The device checks the refraction of light and calculates the optimum lens power for good vision at distance and at close range.

Can presbyopia be prevented?

The natural process of lens hardening occurs in all people and is not hereditary. Nor can it be stopped by special eye training or other measures. Whether and when you start wearing glasses has no influence on the process either. Other eye problems can be partially prevented: How to Preserve Your Vision as You Age

Treatment with reading glasses

Reading glasses make sharp vision in the vicinity possible again. The lenses compensate for the missing refractive power of the presbyopic eyes. The strength of the refractive power is given in the unit dioptres.

With reading glasses, the diopter value is preceded by a plus sign. This means that the spectacle lenses are convergent lenses. They are slightly convex. One says for example: “I need glasses with plus 1.5 diopters”.

How many diopters are needed and when?

The ability of the eye to adjust to close range deteriorates with age. That is why the number of diopters required gradually increases – by about +0.75 diopters every five years. If you have basically healthy eyes and want to read a text at a distance of 35 centimetres, you can use this table as a rough guide:

• 45 to 50 years: reading glasses with +0.75 diopters
• 50 to 55 years: reading glasses with +1.5 diopters
• 55 to 60 years: reading glasses with +2.25 diopters
• 60 to 65 years: reading glasses with +3.0 diopters

In the case of farsightedness, the values must be added together. Example: Up to now, a farsighted person has had corrective glasses with +2.0 dioptres. At the age of 55 to 60 years he needs reading glasses with +2.0 dioptres to correct long-sightedness and additionally for presbyopia +2.25 dioptres = a total of +4.25 dioptres.

For short-sighted people, myopia compensates for presbyopia. Example: A myopic person has -3.0 diopters. At the age of 60 to 65 years the following calculation results: -3.0 diopters +3.0 diopters = 0.0 diopters. He could therefore read without reading glasses.

Most older people need two pairs of glasses, corrective glasses for distance and reading glasses.

Bifocal glasses

The tiresome changing of glasses for the near and far range can be avoided with bifocal glasses. They are adjusted to distance vision in the upper lens area and to near vision in the lower lens area when reading. With conventional bifocal glasses, a visible edge separates the two areas. Disadvantage: The abrupt transition between far and near vision can be perceived as disturbing.

Varifocals

In progressive glasses, the lens is ground so that the two zones for distance and near gradually merge into one another. Advantage: Presbyopia patients can see clearly not only at distance and near, but also in the central area – for example when working at a computer screen. Disadvantages: Some people have problems getting used to the new glasses at first, because wearing progressive glasses can cause slight dizziness and headaches. Some people who wear glasses also have the feeling that the floor in the lateral field of vision bulges upwards. The initial problems usually subside after a few weeks.

What are computer glasses?

Anyone who works a lot and with concentration on the computer may benefit from so-called screen glasses, also called workplace glasses or computer glasses. They contain several different areas that are designed to fit your daily work as closely as possible. For example, the upper section can be adjusted to the screen, the lower section to read documents on the desk. Many employers subsidize computer glasses – provided they are necessary for work, ophthalmologists prescribe them specifically for monitor work and private visual aids are not sufficient.

Treatment with contact lenses

Presbyopia can also be corrected with contact lenses. There are hard or soft contact lenses.

There are also three different principles for improving near vision:

1. Principle of monovision

Most people have a dominant eye. A contact lens for far vision is placed on this so-called dominant eye, and a lens for near vision is placed on the other eye. The brain processes both visual impressions in such a way that with one eye images in the distance are sharp and with the other eye images in the near are sharp. Disadvantage: With monovision, only reduced spatial vision (stereo vision) is possible. Distances – for example when pouring coffee or climbing stairs – are no longer perceived so precisely. Problems can also occur when driving a car. For people who have to make high demands on their spatial vision due to their jobs, these methods are therefore rather not suitable.

2. Bifocal contact lenses

When looking straight ahead you look through the upper part of the contact lens and can see well in the distance. When your eyes are lowered, for example when reading, you look through the lower part for near vision. To prevent such bifocal lenses from rotating in the eye when the eyelids move, they are slightly heavier at the bottom than at the top. In order for this “trick” to work, the lens must be very well adjusted by an ophthalmologist. There are also dimensionally stable, i.e. hard contact lenses that have a lower near vision area that looks like a piece of cake, with the central area in front of the pupil being left out.

3. Simultaneous principle

In the simultaneous principle, the contact lenses have concentric rings arranged around the centre, whose zones provide a sharp image of the different visual distances. It takes the brain a while to get used to the simultaneous principle, because it has to learn to select the desired image – be it far or near – and to suppress the second, equally sharp image. To ensure that the contact lenses fit correctly, it is important that the central area is allowed to shift only minimally.

4. Hybrid forms

Since the brain can learn to assemble images of the right eye with those of the left eye, the principle of monovision can also be combined with the simultaneous principle. One variation is then to place a lens with an inner near vision area on the leading eye and to take a “normal” lens for distance vision for the other eye. The alternative to this: The lenses for both eyes have the near vision range in the middle zone, but the circle is larger in the leading eye. It is also possible, however, to wear contact lenses for far vision and to put on glasses for near vision for reading.

Important: The eyes must be measured by a doctor to ensure that the contact lenses are correctly positioned. The diameter and radius of curvature are just as important as the plastic they are made of – the material can be hard or soft. The ophthalmologist’s office or optician’s branch provides information about the care of contact lenses. They should not be worn longer than recommended. This is because the cornea needs a few hours during the day in order to be optimally supplied with oxygen.

Operative procedures for presbyopia

If the lens of the eye has lost its elasticity with age and has also become cloudy, this is known as a cataract. An artificial lens is usually inserted into the eye as part of the cataract operation that is then necessary. However, such monofocal lenses only sharply image objects at a certain distance from the eye. In most cases, this point is chosen so that the patient can then see well at a distance. To read, they need glasses after the operation. However, for some years now there have been special lenses, so-called multifocal lenses. In the ideal case, these lenses can make reading glasses superfluous:

• Rigid artificial lenses consist of a solid plastic material. Several rings with different refractive power are incorporated on the front surface. This creates two or three zones of sharpness in the eye – for near and far vision. In the intermediate zone, however, the eye sees rather blurred, which makes it difficult to work on the computer, for example. Another disadvantage for drivers: In darkness, reflections can occur around point-shaped light sources – for example, around the taillights of cars in front. The problems of multifocal lenses, which have not yet been completely solved, mean that they do not yet have a large market share in Germany.
• Deformable artificial lenses change their position behind the pupil and thus the refractive power of the eye by the remaining activity of the ciliary muscle. These accommodating interocular lenses are designed to enable near and far vision – but they are also still in the testing phase.

Treatment with laser techniques

As an alternative to reading glasses, a surgical correction is possible. However, an operation is difficult to reverse. It should therefore be well considered. Interested parties should inform themselves in detail about possible side effects and costs. There are two different procedures for treating the eyes:

1. The LASIK method

In the LASIK method, the doctor first cuts a very thin lamella partially from the corneal surface, leaving a small part attached. The lamella is folded over. The relief of the remaining cornea is then redesigned with a high-precision cold light laser (excimer laser) and the flap is then folded back. The lamella acts like a plaster produced naturally in the body, which enables healing within a few days.

The lamella can be formed using two different methods: either with a precision knife (keratome) or with the femto-second laser. The modern laser method is considered to be gentler, safer and usually more comfortable for the patient.

2. Conductive keratoplasty (CK)

It is suitable for presbyopia patients who can see well at a distance and for long-sighted patients with a visual defect of no more than +1.5 diopters. The ophthalmologist marks several points on the cornea according to calculations made beforehand. The treatment is then carried out in the marked areas by means of high-frequency waves which act on the corneal tissue with the help of a small probe. The treatment causes the tissue to contract, similar to the tightening of a belt. After the treatment, the patient can see with the treated eye close up and with the untreated eye sharply in the distance. The method is not yet established.

There are two other methods that are promising, but are still in the experimental phase:

Soft lasering of the lens

For near vision it is important that the lens can become more spherical. In the course of life, however, it increasingly loses its elasticity. Scientists are currently investigating how rigid lenses could be softened with the help of laser pulses. Animal experiments have been successful, but cataracts often formed in the treated lenses. The extent to which the results can be improved and transferred to humans in the future is still open.

Corneal implant

This new surgical method, developed in the USA, is suitable for presbyopic people who can see well at a distance. Similar to the LASIK method, a lamella is cut, but then an implant is inserted instead of being lasered. This is a plastic disc with a diameter of 3.8 millimetres, for example, which has an opening of one millimetre in the middle. The small disc works like a pinhole aperture in a camera lens. This means that the depth of field increases so that objects in the vicinity can be imaged sharply in good light. The implant can be removed again if the result is not satisfactory. This method is also still being tested in clinical studies in order to be able to predict the achievable results more accurately. Here too, side effects are possible, such as clouding of the cornea, scars or poor twilight vision.

Important note: This article contains only general information and must not be used for self-diagnosis or self-treatment. It cannot replace medical advice. Please understand that we cannot answer individual questions.