As we get older, starting at age 40, sometimes we begin to experience changes in vision that indicate that we suffer from eyestrain or presbyopia.
With the advancement of the techniques, this problem of refraction can easily be corrected by surgical intervention.
Monovision is a technique in which the dominant eye is corrected to focus on far and non-dominant vision for near vision. Normally, this is done by maintaining a slight level of myopia in the eye for near vision. The binocular vision (both eyes) then allows a good joint vision, both distance and near and a total freedom from glasses. The most current techniques are called micro-monovision or advanced monovision and we perform them with excimer laser, using the LASIK technique (lamellar surgery) or through LASEK / PRK (surface surgery). We always carry out a preliminary test with contact lenses that simulates the final visual situation and that allows us to know which people can adapt satisfactorily to this technique
Laser Excimer techniques
Laser techniques, specifically designed for the correction of presbyopia, are designed to take advantage of the usual LASIK technique and allow correct close and far vision at the same time. Many times, they are known by the general term of presbi-LASIK.
The most widespread techniques transform the cornea into a multifocal structure in which, generally, the central part is intended for near vision and peripheral part to far vision. In all these techniques, the light is “distributed” between the two spots, the far and the near, which, being opposite, can be translated into an improvement in the next vision accompanied by a slight penalty of distant vision, usually well tolerated.
The ideal candidates for this surgery are the long-sightedness aged between 45 and 55 years, from +1 to +4 diopters and with astigmatisms less than 1 diopter. Patients previously operated with hypermetropic LAKIK who currently have presbyopia may also benefit from it. The technique has evolved so that short-sighted people with presbyopia can also be operated.
Techniques with femtosecond laser
The femtosecond laser is a very sophisticated instrument that we usually use in LASIK surgery for the realization of the corneal flap. When used for presbyopia surgery, a cut is made inside the cornea that produces a change in the central cornea in the form of a moderate curve, so that this area can properly focus up close.
It is a type of surgery that is done from the outside of the eye. It is one of the most recent and advanced techniques and, for the time being, it is reserved for people with a tired sight between 45 and 55 years of age, with low distance prescription (+0.50 to +1.00) and virtually no astigmatism.
Multi-focal lens implants.
The surgery by implanting multi-focal lenses is currently the most used for the correction of presbyopia. In the last few years, it has been prove that, in many cases, is a safe and effective technique for the solution of tired eyesight.
The surgery consists in replacing the transparent lens (natural lens of the eye) with a lens that allows focusing without glasses dependence on both far and near vision. Although technically it is somewhat different, it actually resembles cataract surgery, in which we replace the opaque lens (cataract) with an intraocular lens.
What does the term multi-focal lenses mean?
The term “multi-focal lenses” is used to define different types of lenses (diffractive, refractive, accommodative, asymmetric, etc.), all with the same objective. The choice of one type or another depends on the characteristics of the eye and the visual needs of the person, which are evaluated in the preoperative tests, to decide the ideal lens in each case.
Who can undergo the intervention?
Candidates are people from 45 (farsightedness) or 50 (short-sighted) with any graduation, generally from 2 diopters, with or without astigmatism. It is a stable surgery, which does not require further reinforcement or additions over time and which, logically, by eliminating the crystalline avoids cataract surgery in the future.
When the state of the eye allows it and the visual needs of the patient require it, we also use this type of lens in cataract surgery, in this case, with the double objective of improving vision (by extracting the cataract) and achieving the greater independence of the glasses, both from far and near.
A special situation is that of patients already operated on cataracts, with conventional monofocal lenses and who wish to improve their vision up close. In these cases we implant a second lens, specially designed for this purpose, which provides multifocality and good close vision without glasses. In some cases, techniques with multifocal lenses can be combined with laser techniques.
Corneal implants are extremely thin discs of plastic material with a central hole that are implanted in the thickness of the cornea, to filter the rays of light and provide a precise focus for near vision. These are encouraging techniques, currently under development and applicable in very selected cases, which will be an alternative within the possibilities of surgical correction of presbyopia.