Presbyopia, more commonly called “eyestrain,” is the vision problem that affects the most people. Currently there will be about 1.8 billion people affected in the world, and by 2.3 billion people are expected to be affected by 2.3 billion. Hence, the possibility of solving presbyopia with surgery is one of the new frontiers of ophthalmology.
Presbyopia itself is the loss of accommodation, which is the physiological capacity that allows us to maintain a clear image of an object as it approaches us. Accommodation means an increase in the optical power of the eye, bringing the focal point at a distance closer to a closer reading point. As a practical example, to focus at 33cm from the eye, it is necessary to accommodate 3 diopters.
Symptoms that alert us to suffer from eyestrain
Accommodation decreases with age and by the age of 40 we begin to notice difficulties in reading without the aid of glasses. When we surpass 40 years of age there are more and more difficulties in reading, reaching the minimum accommodation.
There are people who, at the age of presbyopia, are able to read unaided. Although there are many factors that can influence this, it is frequent that they have some defect of myopia or astigmatism. This will mean that they need less accommodation to see well up close, but at the age of presbyopia, even myopes need a different corrective treatment to see well at distance and near.
How presbyopia is treated
Currently, in addition to bifocal and progressive glasses, there are also bi- or multifocal lenses. Among these possibilities there is also the so-called “monovision”, which consists of correcting the dominant eye for distance and the other for near.
In the field of surgery, no method has been able to restore, so far, a true accommodation, in terms of dynamic and variable ability to focus at all distances. There are only some ways to remedy it to a greater or lesser extent, pseudoaccommodation.
Among these methods, bifocal, multifocal and variable focal intraocular lenses (IOL) stand out. It is usually a surgery similar to cataract surgery, exchanging the crystalline lens for an IOL. The near and far optics in the same intraocular lens are superimposed and produce near and far foci on the retina simultaneously. This causes certain limitations in visual quality and often discomfort during night vision, although it is the brain that will ultimately choose the image that interests it at any given moment, so its ability to adapt can compensate for many imperfections.
There are corneal techniques for presbyopia. These range from monovision, with classic laser procedures (Lasik or similar), correcting one eye for each distance, to bi- or multifocal corneal creation (presbyLasik). The disadvantage is that such laser ablative procedures are virtually irreversible.
Intracranial impants can also be inserted into the cornea, lifting a flap (as in the Lasik technique) or creating an interlaminar pocket. The implants can be of a refractive type, such as intracorneal lenses, or in the form of a diaphragm without optical power. This would achieve great sharpness over a wide range of distances.
Can presbyopia or eyestrain be prevented?
Traditionally, certain exercises and nutritional supplements (such as lutein) have been suggested as a method to delay the onset of presbyopia. However, there is no scientific evidence in this regard.
Novel accommodative intraocular lens designs are now appearing that may be useful. The way to truly restore physiological accommodation would be to replace the crystalline lens with a clear, elastic gel to fill the capsular bag. This is not a new idea but, for its practical application, it must still overcome technical problems. Also, with the advent of ultrafast lasers (femtosecond), the possibility of performing surgery on the crystalline lens without affecting its transparency, recovering its elasticity and accommodation, is beginning to be considered.