Presbyopia, what is it?
Presbyopia is a natural age-related phenomenon ; it is a change in near vision which gradually becomes blurred and wearing glasses to read is then essential. It appears around 40 years, increases until 60-65 years to stabilize. The term “presbyopic” appears around 1690 and comes from the ancient Greek “presbutês” meaning “old”!
What are the symptoms of presbyopia?
These signs are numerous and happen without even realizing it. One of the first symptoms will be asthenopia or more commonly all the manifestations linked to the fatigue of the ciliary and oculomotor muscles ; you feel a feeling of fatigue such as eye discomfort, tingling, headache, fixing his attention becomes more and more difficult.
These genes are all the more important when the light is low, we approach the windows, we seek the best angle to be able to read. The most characteristic sign of presbyopia is pulling a document away to read it, the symptom of “arms that are too short”.
Putting on make-up, sewing, tinkering, reading, all activities requiring near vision are becoming more and more laborious, even impossible.
How presbyopia works
Presbyopia is due to the natural decrease with age of the ability to accommodate the lens when reading .
To see up close, crystalline , transparent lens inside the eye, bulges quickly under the action of the ciliary muscle, it thus increases its power of refraction, to form a sharp image whatever the distance on the retina: it is the 'accommodation.
This accommodation is therefore a very rapid movement of the lens and can be compared to the focusing of autofocus devices.
The value of accommodation varies with age: very important in children (12-14 diopters at 10 years old) it is at its maximum around 20 years old (10 diopters) then begins to drop: 6 diopters around 37 years old, 4 diopters at 45 years old to reach 1 diopter around 60-70 years old.
Inevitably, the lens ages with age and loses its elasticity, it hardens. The action of the ciliary muscle on this more rigid lens becomes difficult, the accommodative power of the eye decreases.
Focusing for near vision is no longer done correctly.
In the presbyopic, the accommodative power of the lens decreasing , the image of a close object is no longer on the retina but behind it . The net reading distance increases; we move the text away but the size of the characters limits this distance! Vision at the usual reading distance becomes blurred.
How is presbyopia corrected?
To compensate for this lack of accommodation, near vision must be optically corrected with reading glasses equipped with convex lenses, of positive power, it produces a magnifying effect ; then the image will form again on the retina. Presbyopia is measured in diopters from 0.25 to 0.25 from +0.75 to +3.50.
This correction is determined according to your working distance and your age.
To this defect of near vision, can be added visual defects of distance vision such as myopia, astigmatism or hypermetropia. Then on your prescription appear 2 corrections: that of vision from afar and that of near often noted in the form of an addition.
The correction of presbyopia evolves approximately every 2-3 years; you will then have to take the opportunity to consult an ophthalmologist who will not only check your visual needs and can also detect any other visual condition, glaucoma, AMD, conjunctivitis…