Monovision is the method of using one eye for distance vision and the other eye for near vision. Contact lenses, refractive surgery, and intraocular lenses are all methods used for monovision. When a patient chooses monovision, the dominant eye, or the one that would be used to focus on a camera, becomes the distance eye and the other eye is focused for close vision.
The monovision method works because the brain learns to adapt to which eye sees at which distance. This method is also a form of a concept known as simultaneous vision. There is usually an adjustment period in adapting to this method of vision. Most patients find they are able to adjust. Because surgery is a permanent solution, doctors advise that patients try monovision contact lenses first.
Disadvantages of monovision include a lack of visual sharpness. Persons who require very sharp vision due to a hobby or occupation may not be pleased with monovision results. Another drawback of monovision is that some patients experience decreased depth perception or blurred vision in the eye that focuses on near vision in certain situations.
Some patients report problems with seeing shadows when trying to read small print. Because of these side effects, it might still be necessary to wear prescription glasses for some activities, such as night driving. An advantage of monovision over other options, such as multifocal lenses, is lower cost. Multifocal lenses have separate portions of the lens focused for near vision and for distance vision.
With the popularity of Lasik surgery, which restores a patient’s ability to see without glasses, some patients over 40 years of age may be forced to give up their ability to see close up so that they can see at a distance. Some choose monovision as a compromise.
Presbyopia, the inability of the eye to focus at near, middle, and far distances, occurs in most people around age 45. It is thought to occur because the eye’s natural lens loses its elasticity and the ability to be flexible and focus as it did at a younger age. Presbyopia makes it difficult to read or see at a close distance and usually requires reading glasses. Because presbyopia is a continuous condition, the ability to focus decreases every few years, usually until a person reaches his or her mid-60s.