What is presbyopia?
Presbyopia is associated with reduction of the eye’s accommodative power. Accommodation is the means by which the eye can automatically regulate its focal length to see distance from a short or long distance according to its needs; the process is identical to autofocus in cameras. Reduction on accommodation begins at the average age of 45 years and is ineluctable, reflecting both the enlarging and the hardening of the crystalline lens, processes entailing the lowering of its deformability.
Presbyopia increases progressively and is stabilized towards the age of 60 years.
When isolated, it is corrected by means of convex lenses; when associated with other visual impairment, it is corrected by means of progressive lenses (different long and short-distance vision). It can only be surgically corrected using lase
Choice of a technique for surgical treatment of presbyopia depends on the visual impairment possibly associated with the presbyopia.
In the myopic patient, presbyopia is treated by partial correction of the myopia on the non-dominant eye (residual myopia from -1.5 to -2 diopters) and by total correction of the myopia on the dominant eye (swing technique or monovision through which the master eye is corrected for distant vision and the non-dominant eye for near vision). According to associated visual impairment and to the patient’s age, the correction is carried out by either laser (Lasik) or implant.
Emmetropic presbyopia or weak hypermetropia (up to +3 diopters) is most often corrected by laser. Correction can be carried out using the swing technique (with the dominant eye corrected for distant vision and the non-dominant eye for near vision with induced myopia of -1.5 to -2 diopters) or by multifocality (“PresbyLasik” technique, through which each eye is corrected for both near and distant vision). The choice of either swing or multifocality is determined according to the case and by the habits of a given surgeon.
Correction of presbyopia in cases of strong hypermetropia is generally carried out by means of multifocal implants and usually after 50 years of age (loss of physiological capacities of accommodation by the natural crystalline lens).
When presbyopia and astigmatism coexist, laser techniques facilitate precise correction of the astigmatism and are preferred to implant techniques.