Presbyopia or eyestrain is the progressive decrease in the eye’s ability to focus up close due to the loss of elasticity of the crystalline lens. It appears in all people with advancing age, usually after the age of 40 or 45.
Initial symptoms of presbyopia
The initial and common symptoms of presbyopia are the need to move away from what we are looking at and what we are looking at to be able to see it clearly and the need for more light for tasks in close proximity.
With presbyopia, the eye prescription, i.e. the number of diopters to perfectly focus the vision, for distance and near vision, will no longer coincide. This will be the moment when the Ophthalmology specialist will start prescribing progressive or multifocal glasses or contact lenses, so as not to have to wear two different prescription glasses all the time.
Presbyopia and farsightedness or nearsightedness
Distance vision can also worsen with presbyopia if the patient has a hyperopic defect.
Conversely, a myopic deficiency delays the symptoms of presbyopia, since the myopic eye at rest is focused at close range. On these occasions, in order to be able to read near clearly, myopes with presbyopia must remove their glasses and put them back on to focus well at distance.
Refractive surgery for presbyopia
Being a visual pathology with a high incidence in the population, for years there have been attempts to find definitive solutions to avoid the discomfort it causes.
In addition to the use of glasses or multifocal contact lenses, one of the treatment options is refractive surgery. With the passage of time, techniques that initially promised to have good results have finally been discarded, and on the contrary, others are being incorporated in recent years. Laser corneal treatments have been suggested to generate multifocal corneas with greater or lesser success, but in most cases the improvement in vision has been accompanied by a certain worsening of distance vision. This situation, together with the fact that it is irreversible, has meant that acceptance has not been high.
Something similar is intended with conductive keratoplasty which, through a thermal effect by radio waves, generates a change in the curvature of the cornea and in its dioptric power. The disadvantage of this technique is that it is usually temporary.
Some years ago the Schachar technique was used, which consists of incisions in the sclera and the application of scleral implants, but it has been discarded due to the reversion of the initial result after a short time.
Another surgical technique is monovision, in which one eye is corrected for near vision and the other eye for far vision. It should be checked beforehand whether the person will be comfortable with this situation and it can be simulated with contact lenses for a few days. Normally, the “dominant” eye is used for distance vision and the “non-dominant” eye for near vision. Not everyone is able to tolerate it, but it is still one of the most commonly used today.
Another method is intracorneal microlens implants or devices to optimize near focus. These implants are relatively recent and are usually recommended for only one eye, since distance vision suffers.
Finally, there are two types of intraocular lenses that improve the symptoms of presbyopia:
- Diffractive pre-crystalline lenses: they are placed in the space between the iris and the crystalline lens. They have been developed recently, so there are few published studies on them, but even so the initial results obtained are very promising, with the advantage of being a reversible technique.
- Multifocal posterior chamber lenses: they are placed behind the pupil after removing the crystalline lens, in the same way as in cataract surgery. They are by far the most widely used in recent years, since their effect lasts for the rest of life, and the implantation technique, the same used for cataracts, is the most frequent surgery that surgeons are most accustomed to performing. In addition, they allow a very high quality of vision and independence from glasses. They can also correct, in addition to presbyopia, any previous refractive defect such as myopia, astigmatism or hyperopia. There are also specific multifocal intraocular lenses to be implanted in eyes that have already undergone cataract surgery. Thanks to them, it is possible to obtain independence from distance and near glasses in the vast majority of patients.
It is important to note that all of the above techniques serve to improve or suppress the visual symptoms of presbyopia, but do not return the elasticity of the crystalline lens to the eye as it was in youth, which would be the perfect treatment for presbyopia.
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