Presbyopia is an age-related eye condition that makes near vision more difficult or even impossible as the age increases. This condition usually appears between the ages of 40 and 45, and progresses until the age of 60.
What causes presbyopia?
Up to the age of 40, approximately, the crystalline lens – the lens behind the iris that allows focusing in near vision – is flexible, so that, by changing its curvature, it allows focusing on distant and near objects.
However, after the age of 40, the crystalline lens loses elasticity, becoming more rigid. This means that it cannot change its shape to focus on objects located 30-50 cm away (near vision). It is common, at first, to move the near object farther away in order to see it more clearly but, with time, this will not be enough and one will have to resort to corrective glasses for near vision. This is true for patients who do not have refractive defects in distance. On the other hand:
– In myopic patients and in some cases of astigmatism, they will only appreciate presbyopia if they wear their glasses or contact lenses. However, without them, they will see well up close.
– In hyperopes, the opposite will happen, so that presbyopia will appear earlier, increasing, in some cases, the distance refractive error.
Treatments available for eyestrain
Near glasses are the most common and easiest way to correct the symptoms of presbyopia and will be used for all activities that require near vision such as reading, sewing, etc.
There are also bifocal and progressive lenses. Bifocals have one focus for distance and another for near, so that middle distance vision (computer) will not be satisfactory. Progressive lenses, as their name indicates, have multiple focuses, so that we can see correctly in the middle distance. This type of glasses is recommended for people who need to wear optical correction for distance vision and do not want to take them off or exchange them for others for near vision.
Another option would be multifocal or progressive contact lenses, which do not work well in all cases, but may be a useful option for some patients.
Nowadays, there is also the possibility of surgical treatment to correct this problem. There are some laser treatment techniques for presbyopia, such as conductive keratoplasty. However, these techniques are not sufficiently developed, so that they offer results that diminish over time or are not predictable in terms of the quality of the final result.
The surgical technique currently used to correct presbyopia is the refractive exchange. This surgery replaces the crystalline lens, which has become rigid, with an artificial lens that corrects the symptoms of presbyopia, providing multifocal vision.
What is refractive exchange and how does it cure presbyopia?
The surgical technique used for this procedure is the same as in cataract surgery, with the difference that, instead of implanting a monofocal intraocular lens -which allows good distance visual acuity without having to wear glasses, although close-up vision will be necessary-, a multifocal lens is implanted. In this way we can have good distance visual acuity, intermediate vision and near vision without having to wear glasses.
At present there are basically two types of progressive intraocular lenses: multifocal and trifocal, which have appeared in recent years.
A thorough study of the optical conditions of the patient’s eyeball will make the ophthalmology specialist decide on one or the other. Likewise, both types of lenses can correct astigmatism associated with myopia or hyperopia.
In which cases can refractive exchange be performed to treat presbyopia?
The ideal candidate for this type of surgery is the person who needs to wear glasses, both for distance and near.
Probably the ideal patient will be the hyperopic patient with more than one diopter for distance, since he/she will experience a great improvement in distance and near vision. The myopic patient will gain a lot in distance vision. However, near vision will require light to see in better conditions. Let us not forget that, if the myopic patient removes his glasses for distance vision, he will see quite well up close, especially if his myopia is two or four diopters.
Nowadays cataract surgery is a very safe and effective surgical procedure. At the same time, in some patients the implantation of these multifocal lenses may generate night halos, especially when driving at night. However, the new generation lenses are minimizing this problem, so it is very rare that this will end up being a major problem for the patient.
Finally, it should be noted that it is an effective and safe technique and, in the right patients, it is very useful, with all research showing that patient satisfaction is very high.