It is a physiological visual condition that occurs in middle-aged people who can not focus on nearby objects.
Why does presbyopia occur?
Presbyopia occurs as a result of progressive weakness related to age. Accommodation is the process by which the eye adapts to obtain a clear image of nearby objects (less than 6 meters away).
When a person focuses on a nearby object the ciliary muscle of the eye contracts, which produces a change in the shape of the lens, so that the light of the object focuses on the retina instead of behind it.
At greater distances no accommodation is required since light from distant objects focuses on the retina anyway (in people who do not have refractive errors).
Therefore, the adaptation process guarantees that a person has a clear vision at all distances.
In people older than 40 years, the lens becomes less flexible; therefore, its ability to change its shape is reduced.
This rigidity of the lens increases progressively; therefore, the degree of presbyopia gradually increases until the age of 60, when there is a total loss of accommodation.
what are the signs and symptoms?
Presbyopia usually begins around age 40. However, many people develop symptoms even in their 30s.
People notice a growing difficulty in performing visual tasks nearby, especially at night.
They also notice that they can read or write if the material is kept at a distance farther from the eye than they are used to.
Attempts to perform visual tasks near normal distances cause eye fatigue and headaches.
Initially, the difficulty is only for reading objects at a distance, but as age advances, difficulty is experienced even for intermediate-distance tasks, that is, computer work, reading labels in stores, cooking, as well as for barbers , beauticians and tailors.
Many people gradually avoid nearby tasks and, for professionals, labor productivity can be affected.
People who have myopia notice that they experience the above symptoms while wearing their glasses, but they feel extremely comfortable with nearby tasks after removing their glasses. On the other hand, people with hyperopia have an earlier onset of symptoms compared to others without refractive errors.
How is it diagnosed?
Presbyopia is diagnosed by a simple eye examination that includes a vision test with an eye chart and refraction.
In addition, a complete routine eye exam is performed with a slit lamp and an examination of the retina after dilating the eyes.
When do you get premature presbyopia?
Presbyopia that occurs at a much earlier age than expected is called premature presbyopia.
Causes include uncorrected hyperopia, malnutrition, trauma, excessive demands for near vision, diabetes, multiple sclerosis, cardiovascular disease, myasthenia gravis, anemia, alcohol intake, surgical removal of the lens, and ingestion of medications such as antidepressants, antihistamines, and diuretics .
How do you correct presbyopia?
There are several ways to correct presbyopia. The most common and the most popular is through the use of glasses. When using glasses, it must be remembered that the same power can not be used for both far and near vision.
A person who has presbyopia and who does not have any refractive error requires a lens with more power only for near vision.
You can see well at a distance without any power. A person with myopia needs a lens with less power for distance and a different power for the near one.
A hyperope (a person with hyperopia or what is commonly known as farsightedness) requires additional power for distance and additional power for closeness.
In other words, the near correction is the algebraic sum of the distance correction and the additional power.
In the early stages of presbyopia, people can see objects at an intermediate distance with distance correction; however, as age advances, they require a correction for the intermediate distance that is slightly less than the reading power.
The lenses for correction of presbyopia can be presented in different ways:
- Single vision reading glasses: The power in the glasses is for tasks close to the whole objective. Therefore, while near vision is clear while wearing the glasses, the person would have to remove the glasses for distance vision.
- Bifocals: Here there is power for far vision at the top of the lens and for near vision at the bottom of the lens (reading segment).
The reading segment can be curved, D-shaped or rectangular, and the partition line is visible. Bifocals do not provide clear intermediate distance vision.
- Progressive (progressive addition lens): Here is a gradual continuous change of power from the top to the bottom