The use of one eye for distance vision and one eye for near vision is referred to as monovision and is one of the options to consider as part of your refractive surgery decision if you are over age 40. Monovision has been used successfully for over 20 years with contact lens correction and with various types of refractive surgery. By correcting one eye to focus for distance and one eye to focus for near, the vision part of our brain tends to suppress or filter out the image from the eye that is not in clear focus. The eye that is not in focus usually does not bother the patient.
One of the best ways to define monovision in the context of refractive surgery is that you can aim to have each eye corrected to focus at any distance you choose. How well it will see at other distances depends upon how old you are. For example, if you are 30 and we correct each eye to excellent distance vision, then you will have good vision at almost any distance because, due to your young age, your eyes will be able to accommodate (adjust focus) for near vision tasks. If, on the other hand, you are over 40 and we correct each eye to excellent distance vision, you will not see well at a typical reading distance and will need reading or near vision glasses. This change in accommodation (focusing ability) will generally begin to be noticed around age 40 and will usually become significantly worse over the next few years (presbyopia). This loss of ability to change your focusing distance from far to near (presbyopia) will occur whether or not you have refractive surgery. At any age, if you have the vision in one eye corrected to focus for near tasks such as reading, you will not see clearly with this eye for distance.
As a general rule, however, we suggest against monovision if you are under age 35 for two reasons:
1) It will be a number of years before you will notice any benefit
2) It is very possible that there could be a better (or at least as good) surgical way to help presbyopia by the time it becomes a problem for you.
We also generally recommend against monovision at any age for people who may need to see above average for tasks at a particular distance, such as pilots, race car drivers, anyone who drives for a living (especially at night), and avid tennis players (especially for night playing).
We create monovision using the laser such that the dominant eye focuses at distance and the non-dominant eye focuses at near. The brain typically adjusts to each eye being focused at a different distance within 6-8 weeks. You do not need to consciously make any adjustments.
There is no right or wrong answer to the question of whether to have monovision. We hope that this information is helpful in making this decision.