Presbyopia (also presbyopia) is a refractive error in which the lens of the eye loses elasticity, which makes it difficult to focus on nearby objects.
Presbyopia usually occurs between the ages of 40 and 45, sometimes very suddenly.
It is physiological and part of the natural aging process of the eyes.
Presbyopia and accommodation
For the sharp imaging of the objects, the refractive power of the eyes must be adjusted (accommodation). This means that the lens changes its strength.
The ciliary muscles are connected to the retaining ligaments attached to the two ends of the lens.
If these muscles contract, the lens becomes thicker and more curved, consequently the light rays emanating from the nearby objects are clearly imaged on the retina.
The lens becomes more rigid and less elastic as you get older.
This makes it difficult to change the shape of the lens.
With the lens in a neutral position (relaxed ciliary muscles) you can see the objects in the distance sharply.
Classification of presbyopia
There are five types of presbyopia:
- Onset of presbyopia – a very early phase. It affects people between 40 and 50 years of age; in good lighting conditions you can still see nearby.
- Secondary presbyopia – caused by diseases, such as poisoning.
- Absolute presbyopia – occurs from the age of 50 with stabilized accommodation error, the eyes can no longer concentrate on nearby objects.
- Premature presbyopia – this means that it starts before the age of 40, for example at the age of 30 or 35.
- Nocturnal presbyopia – you can’t focus on nearby objects in low light.
What are the causes of presbyopia?
Presbyopia is caused by age.
This distinguishes them from astigmatism, myopia and farsightedness, which are related to the shape of the eyeball and are caused by genetic or environmental factors.
Presbyopia is thought to be caused by a gradual increase in strength and loss of flexibility of the lens.
These changes occur in the proteins of the lens, making them more rigid and less elastic.
Changes also occur in the muscle fibers that surround the lens.
With less elasticity, the eye has difficulty seeing sharply nearby.
Signs and symptoms of presbyopia
A sign of presbyopia is the need to keep magazines, books, or other things to read up to the entire length of your arm so that you can see them sharply.
Symptoms of presbyopia include:
- red eyes;
- difficulty seeing sharply;
- tired eyes;
- blurred vision at normal reading distance;
- squinting your eyes to see nearby objects clearly;
- Reduction of the ability to concentrate on nearby objects.
Diagnosis of presbyopia
Presbyopia is detected by a complete examination at the ophthalmologist and by an assessment of dilated pupils.
Examinations and tests are recommended after the age of 40 to detect presbyopia.
Treatment of presbyopia
The aim of the treatment is to find a solution to compensate for the inability of the eyes to focus on nearby objects.
If the eyesight was good before the development of presbyopia, you can use reading glasses without a doctor’s prescription.
The commercially available over-the-counter reading glasses are classified on a scale that corresponds to the degree of magnification (diopters).
The less strong glasses have a value of +1.00, the stronger ones of +4.00 excellent.
When should you buy reading glasses?
You should try different strengths until you can read comfortably at the right magnification.
To try it out, you should try to read a text at a distance of 35-40 centimeters.
Corrective lenses are prescribed for presbyopia, if the over-the-counter glasses are not suitable or if corrective glasses are already used, e.g. for:
You can choose from:
- Reading glasses. If the patient has a visual impairment, one can use glasses that are prescribed specifically for reading.
- Glasses with bifocal and progressive lenses. These glasses come in two types — with a horizontal visible transition line and without a transition line (progressive bifocal glasses).
When looking through bifocal lenses at eye level, the lenses correct the view into the distance. This correction gradually changes in the lower part, so that you can see well nearby.
These glasses are very expensive. Therefore, many people buy two pairs of glasses: one for proximity and one to see into the distance.
- Glasses with trifocal and progressive lenses. These glasses are used for correction nearby, at medium distances – such as in front of a computer monitor – and at a distance.
Trifocal glasses may have visible transitions or progressive lenses.
- Bifocal contact lenses. Bifocal contact lenses or bifocal glasses correct vision in the distance and nearby.
You have to place the bifocal lens correctly in the eye, because the lower part is used for reading. This type of contact lens is usually difficult to use and often does not bring good visual success.
The new types of bifocal contact lenses allow distance correction over the edge of the lens, whereas the correction in the vicinity is carried out via the central part.
The first results with these lenses are encouraging.
Monovision with contact lenses
This type of lens is based on the premise that each of us has an eye that dominates over the other.
The dominant eye is the one you use when looking through the viewfinder of a camera to take a photo.
With monovision lenses you wear:
- a contact lens to see into the distance with the dominant eye;
- a contact lens to see nearby with the non-dominant eye.
With this choice you wear:
- a bifocal contact lens in the non-dominant eye,
- a contact lens to see with the dominant eye in the distance.
Both eyes are used for seeing into the distance and only one eye for reading.
The brain learns which lens to prefer, depending on whether you’re looking at objects near or far, so you don’t have to think about which eye to use.