Monovision
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Monovision is a vision correction method used to counteract the effects of presbyopia, thus affecting individuals over 40 years of age. It involves correcting each eye differently to prepare one eye for distance vision and the other for near vision. In short: one nearsighted eye and one farsighted eye are artificially created. Not all patients see well using eyes calibrated in this manner, which is why the decision for monovision correction is not made hastily.
Myopia is one of the most common vision defects.
The dominant eye is corrected for distance, the other for near vision.
Presbyopia involves accommodation problems that affect nearly 10 million Poles over forty. It manifests, among other things, as difficulty focusing vision while reading. The weakening of accommodative muscles is not related to a developing vision defect but to the hardening of the natural lens – it loses its elasticity. This process cannot be stopped; it is a matter of time and individual predisposition until we feel that our “arms are too short for reading.” Presbyopia is most often diagnosed after the age of 40, with its greatest intensity occurring between 40 and 55 years of age.
One pair of eyes, many glasses – the daily challenge of presbyopia
Individuals struggling with presbyopia most often reach for glasses. Some choose separate glasses for near and distance vision, while others opt for progressive lenses, which allow for simultaneous correction of distance, near, and intermediate vision.
Often, a person simultaneously dealing with a vision defect and presbyopia is forced to wear several different pairs of glasses daily, depending on the activity, and if they also play sports – contact lenses. Such juggling of corrective glasses and contact lenses can be truly unbearable.
Course of the Procedure
Before the procedure, a contact lens trial is conducted, tailored to the patient’s needs, as a simulation of the possible outcome. This trial lasts for one to two weeks, and based on its results, it is assessed whether the monovision procedure is a suitable option for the patient.
For monovision, the patient undergoes surgery using the Femto-LASIK method, phakic lens implantation, or lens exchange. All methods correct the dominant eye for distance vision and the non-dominant eye for near vision.
Qualification for Monovision
Monovision, which involves correcting one – the dominant eye – for distance vision (the dominant eye is the one you would use to aim if given a weapon), while leaving the other eye nearsighted, is an optical setup that seems at least strange to patients. How can each eye see differently? The patient suddenly becomes anisometropic. Of course, anisometropia occurs naturally in people. Many individuals suffering from, for example, myopia have different spectacle or contact lens powers in each eye. The Prince of Poets, Johann Wolfgang Goethe, had congenital monovision, which is why this condition is referred to as “Goethe’s vision” in German-speaking countries today.
However, in the case of monovision discussed in this article, this anisometropia is created specifically and artificially.
The decision of which eye will be farsighted and which will be nearsighted is made after a series of tests. It is by no means dependent on the arbitrary decision of the doctor or patient. Before the ophthalmologist proceeds with presbyopia correction using the monovision method, qualification examinations are conducted to check whether the patient’s brain will accept such a solution. In other words, it is verified whether the planned anisometropia will be acceptable to the patient and if they will feel comfortable with it.
This sequence of actions means that monovision correction is not performed if the patient does not pass the qualification examinations and is not 100% certain that monovision is not only tolerated but also provides comfortable vision. Attempts to improve vision using the monovision method can be made repeatedly by searching for ideal contact lenses. Once the eye adapts to this type of correction, the patient can decide to undergo monovision using a laser method.
After a well-performed monovision correction, the brain integrates the images from both eyes, allowing for good near and distance vision (so-called all-round vision). It is worth noting that within monovision, the diopter difference between the nearsighted and farsighted eye can be adjusted depending on the patient’s tolerance and needs, and maximally individualized.
Monovision Procedures
Monovision can be performed in various ways: with contact lenses, through laser vision correction, or with intraocular lens implants. It involves the patient wearing a contact lens/having an intraocular lens implanted for near vision in one eye, and a lens for distance vision in the other.
If we were previously nearsighted, during presbyopia correction in one, usually weaker, eye, the doctor will leave a partially uncorrected defect, known as a residual defect. If we were farsighted, our defect will be slightly overcorrected. Monovision can be divided into three types, depending on what defect remains in the weaker eye adapted for near vision:
- Monovision (the near eye has -1.25 to -2.50 diopters)
- Micromonovision (the near eye has up to -0.75 diopters)
- Minimonovision (the near eye has -0.75 to -1.25 diopters)
Monovision Procedures
Surgical monovision is reversible, but it requires another surgical procedure. If neuroadaptation does not occur after the procedure and the existing difference between the eyes hinders daily functioning, there is no alternative – it must be performed.
Applicable in all surgical techniques:
- Refractive lens exchange.
- Laser vision correction: PRK, LASEK, LASIK, FemtoLASIK, micro-lens vision correction)
- Phakic lenses
Important Information
The separation of eye functions is usually well-received – the eyes cooperate perfectly, and the overall image is clearly perceived by the brain. Although there are some effects on spatial vision, they are not detrimental to most activities. Depending on the patient’s wishes and personal preferences, during the initial examination or lens simulation, the patient can determine whether this method is suitable for them.
In every case, the brain always needs time to adapt to new conditions. If the result of the procedure is not fully satisfactory, the eyes can later be adjusted for distance vision. Reading glasses would then be needed for near distances.
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