What is presbyopia?
Presbyopia is a natural phenomenon linked to age; it is a change in near vision which gradually becomes blurred, and wearing glasses for reading then becomes essential. It appears around the age of 40, increases until 60-65 years old, and then stabilizes. The term "presbyope" appeared around 1690 and comes from the ancient Greek "presbutês" meaning "old"!
What are the symptoms of presbyopia?
These signs are numerous and appear without us even noticing. 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 sensation of fatigue like eye discomfort, tingling, headaches, and concentrating becomes increasingly difficult.
These discomforts are all the more significant when the light is dim; one moves closer to windows, looking for the best angle to be able to read. The most characteristic sign of presbyopia is moving a document away to read it, the "arms too short" symptom.
Applying make-up, sewing, DIY, reading, all activities requiring near vision become increasingly laborious, or even impossible.
How presbyopia works
Presbyopia is due to the natural decrease with age in the lens's ability to accommodate during reading.
To see up close, the lens, a transparent lens inside the eye, quickly bulges under the action of the ciliary muscle, thereby increasing its refractive power, to form a sharp image at any distance on the retina: this is accommodation.
This accommodation is therefore a very rapid movement of the lens and can be compared to the focusing of autofocus cameras.
The value of accommodation varies with age: very high in children (12-14 diopters at 10 years old), it is at its maximum around 20 years old (10 diopters) then begins to decrease: 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 and loses its elasticity, becoming harder. The action of the ciliary muscle on this more rigid lens becomes difficult, and the eye's accommodative power decreases. Focusing for near vision is no longer done correctly.
In presbyopic individuals, as the accommodative power of the lens decreases, the image of a close object is no longer formed on the retina but behind it. The clear reading distance increases; one moves the text further away, but the character size 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, which produce a magnifying effect; then the image will again form 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.
In addition to this near vision defect, long-distance vision defects such as myopia, astigmatism, or hyperopia may also be present. Thus, your prescription will show 2 corrections: one for distance vision and one for near vision, often noted as an addition.
The correction for presbyopia changes approximately every 2-3 years; it will then be necessary to consult an ophthalmologist who will not only check your visual needs but also be able to detect any other visual conditions, such as glaucoma, AMD, conjunctivitis, etc.
