Around the age 40 for many the eye will gradually lose the ability to accommodate, or change focus from distance vision to close up. This condition is known as presbyopia, and is the reason many require reading glasses or bifocals. A technique called monovision can correct one eye (the dominant one) for distance vision, while (if necessary) correcting the other for intermediate or near vision.
The main goal of monovision is reducing the patients need for corrective eyeware for for reading and close up activities. The technique relies a bit upon the brain to filter out the image from the eye which is not in clear focus.
Needless to say, monovision is not for everyone. It takes awhile to become accustomed to it, and approximately 6-8 weeks for the brain to adjust to each being at a different focus. Monovision may result in the loss of some degree of depth perception, and in some cases can cause reduced peripheral focus. Those with very active lifestyles may find monovision is not the right answer for them.
The monovision technique is accomplished through either contact lenses or refractive laser eye surgery such as LASIK. Many physicians will recommend that patients first try the contact lenses and evaluate the results before opting for the more permanent laser eye surgery.