At first glance, monovision seems very strange. But unusual as it seems, most people receive amazing results. Here's how it works:
We all have a dominant eye as well as a non-dominant eye. (You can quickly determine eye dominance with this quick eye dominance test.) When we look into the distance, we are actually using the vision from the dominant eye more than we are using the non-dominant eye. The non-dominant eye still functions, but the dominant eye sort of takes over. Our brain pays more attention to the visual information received from the dominant eye. So if the non-dominant eye is fitted with a near-powered lens to correct our near vision, our distance vision will not be disturbed that much. Monovision, then, involves wearing a contact lens on the non-dominant eye to correct near vision, and a contact lens on the dominant eye (if needed) to correct distance vision. Monovision works because the brain is tricked into thinking that the contact lens is actually a part of the natural eye. (For this reason, monovision does not work in an eyeglass prescription for most of us.) Although it takes a week or 2 to adapt to monovision, it beats reaching for reading glasses every time you want to read. Interestingly, patients who have enjoyed monovision with their contact lenses may be able to enjoy the benefits of monovision LASIK. Monovision LASIK aims to achieve the same corrected vision that you receive from monovision contact lenses, without the contact lenses in your eyes. In monovision LASIK, one eye is corrected for distance and the other for near.
Are you a candidate for monovision?
Although monovision does not work for everyone, it is a viable option for patients who have presbyopia. Monovision can help you achieve good, functional vision at distance and near. It is not "perfect" vision, however. There is usually some compromise between clarity at distance or near to allow patients to fully adapt to monovision while at the same time providing adequately corrected vision. As a result, patients who require the sharpest corrected vision possible at distance or near may not be the best candidates for monovision. Furthermore, monovision may decrease depth perception, which could affect athletic or job performance. The best way to determine if monovision might work for you is to ask your eye doctor.
Source: American Optometric Association, Monovision. 3 Nov 2007.