During childhood, people with normal vision have the ability to focus on objects as close as their nose and also on objects very far away. They can rapidly, without conscious thought, switch focus from near to far vision. This is called accommodation. As each year passes, that ability to focus and to switch focus decreases. By the time most people reach their forties, they need an aid, such as reading glasses or bifocals, to focus on objects close up. This condition is called presbyopia.
Monovision is a technique where one eye (usually the dominant eye) is corrected for clear distance vision, and the other eye is corrected for comfortable near vision. Monovision allows a person to see close objects clearly with one eye and distance objects clearly with the other eye. The vision part of the brain tends to filter out the image from the eye that is not in clear focus, so those who have monovision eventually do not pay attention to the eye that is not as clearly focused. Those who have monovision are often able to see well enough both at distance and near to do things at any age without corrective lenses.
Monovision can be achieved with contact lenses, or with cataract surgery or LASIK, by correcting the non-dominant eye for near vision and the dominant eye for distance vision. If you are considering a vision correction procedure, your doctor can put you into monovision contact lenses so you can try it before you permanently correct your eyes with monovision.
For those undergoing cataract surgery who are considering the intraocular lens for monovision, an in-depth discussion with your doctor is necessary to be sure that this is the correct decision for you. Another alternative that is extremely successful is the ReSTOR® Premium lens implant, which corrects for distance and near vision in BOTH eyes, reducing the dependence on glasses.