As years pass by it’s a natural occurrence to perceive a shift in our vison capacity, after the age of forty we start to find hard reading a book in close proximity and we tend to move the newspaper or the book further and further away from our eyes. This problem is known as presbyopia and it’s a natural occurrence due to the physiological aging process.
What is presbyopia?
The eye is incredibly sophisticated and is made of different structures; in the anterior part of the eye we find the cornea, an organ on which we operate for a variety of refractive issues which have been discussed in earlier articles. The cornea funnels and projects light onto the retina where photoreceptors convert light signals into chemical messages that are then interpreted by the brain as images. After passing through the cornea and before reaching the retina light passes through another structure, the lens, this organ’s job is to focus light rays onto the retina. The lens in fact changes its shape according to the distance of the object we wish to focus thanks to the accommodation process, this process allows us to see sharply at any distance. Presbyopia occurs when the lens loses to a certain degree the capacity to focus, this typically happens due to an excessive rigidity of the structure or impairment of the muscles involved with accommodation. It’s evident that this in process the cornea is not involved, so if this issue arises after laser-eye surgery for refractive defects (myopia, astigmatism, hypermetropia) it has nothing to do with the precedent defect or the surgery.
How to treat Presbyopia
Until recently presbyopia was typically treated with the use of reading glasses. Monofocal glasses are used when there aren’t other refractive disorders, these lenses allow to focus objects positioned near the eye but don’t allow objects in the distance to be focused. In addition to presenting the classic disadvantages of glasses these glasses have the defect of allowing sight only at a preestablished distance according to the focal point set by the lens. The multifocal glasses are used instead when in addition to presbyopia the patient presents other refractive disorders, these glasses enable the eye to have more than one focal point at different distances, unfortunately these glasses require an adaptation phase and have the disadvantage of producing astigmatic aberration areas in the peripheral part of the lens granting the user a poor vision quality.
Overall all therapeutic procedures created to treat presbyopia fall short of giving the patient a perfect result. In most cases the patient must accept a compromise between being able to have distant-sight vision and near-sight vision. This compromise is due to the fact that the loss of the lenses’ accommodation process is never recovered.
From a surgical point of view there are different option when it comes to presbyopia treatment, in summary you can decide if to choose a laser-eye approach or an intraocular approach. The intraocular surgery consists in removing the lens that has lost its accommodation capacity and implanting a multifocal lens that acts as an artificial lens. This technique has the advantage of being able to remove concurrent cataract (the technique involved in both surgeries is the same).
The focal points pf the multifocal lens allows the patient to have a discreet sight autonomy at every distance, but never a perfect vision; the use of glasses will always be necessary for near or distant sight according to the subject. This is a compromise that must be taken into account before deciding to follow through with the surgery, perfect eye-sight is not achievable. Furthermore, many patients experience side effects such as halos in the vision and the presence of distorted light perception.
My belief is that multifocal lenses implants are indicated for specific categories of patients such as older people who already suffer from cataracts, don’t often drive at night and don’t mind having to read with glasses.
My preferred therapeutic procedure is the Monovision Femto-LASIK, this technique uses the refractive laser-surgery technology. The laser is the same one used for the correction of refractive defects such as myopia, astigmatism and hypermetropia and can be utilised to correct presbyopia. In those instances, in which a patient suffers from more than one refractive defect, it can be used to better vision in near-sight and in far-sight. This technique is less effective in patients who are emmetropic (have perfect far-sight) and are suffering only of presbyopia, in these patients the surgery will be monocular.
The Monovision Femto-LASIK exploits the principle that we have a dominant-eye and a non-dominant-eye. Before the surgery we check which is the dominant-eye for it is the most adapt to far-sight vision.
This technique consists in performing surgery on only one eye to create a specialized eye for far-sight vision (the dominant-eye) and an eye specialized in near-sight vision (non-dominant-eye). Thanks to Laser treatment we can empower this eye-specialization, mostly eliminating the need for glasses, having a “good” eye for every situation.
The treatment will never be quite definitive because it will treat the level of presbyopia existing at the time and because presbyopia progresses until 60-65 yrs you can experience the problem again years after the surgery.
This technique is not suitable for everybody, in fact for the surgery to be successful the patient must have a dominant-eye with a good far-sight and good adaptivity skills.
As a rule when it comes to presbyopia it’s a good idea to contact a specialized ophthalmologist that can suggest the best treatment according to individual’s necessities. Not all surgery procedures are suitable for everybody and a medical examination is needed to correctly assess which therapeutic procedure will majorly benefit the patient.
It’s important to understand that whilst myopia, astigmatism and hypermetropia can be completely corrected, with presbyopia you will always have accept a compromise ( which can suit some but not others) because a perfect vision with both eyes is not obtainable.