Presbyopia is a condition that begins around the age of 45. Accommodation is the eye's incredible ability to change focus from distance to near and back to distance instantaneously. As accommodation worsens, people can become very frustrated by the need to put on glasses or remove them in order to see properly when reading or doing work that requires near sight.
Monovision is an option that tricks your brain into seeing both near and distant objects well. One eye is treated for distance seeing, and the other is treated for near seeing. The brain is then able to adjust automatically to use the appropriate eye depending upon the distance of the object you’re viewing.
Monovision can be achieved with contact lenses or with surgery. (Unfortunately, it rarely works only with glasses.) People who are having LASIK or cataract surgery, can opt to be simultaneously treated for monovision. A patient over 45 years old can receive monovision and put their reading glasses away. I usually only recommend monovision to my cataract patients if they have previously tried it and liked it while wearing contact lenses. Once the cataracts get bad, it's difficult to assess whether monovision is working. Monovision means you never have perfect distance vision or perfect reading vision since only one eye does the work for each task. It’s a sacrifice that many people decide to make in order to have some independence for both distance and near seeing. For people who find it necessary to put on their reading glasses every time they need to read their watch, a price tag, or the numbers on their cellphone, monovision can be terrific.
Of course, there may be some activities that still require glasses. Generally, with monovision, you can be free of glasses for 95% of your activities. However, if you’re driving home at night, for example, which requires exceptional depth perception, you may need to wear glasses that provide your non-dominant eye with better distance vision. If you want to read a novel, you may need to wear glasses that provide your dominant eye with better near vision in order to prevent your non-dominant eye from tiring too quickly.
The dominant eye’s vision is the most important. If distance vision in the dominant eye is unclear, the patient will be unhappy. The most common reason for touch-ups after surgical monovision is a lack of perfect vision in the dominant eye. Remember though, the brain and the eye notice no difference between monovision with contact lenses, LASIK surgery or cataract surgery. If you expect perfect distance vision and perfect near vision, however, monovision will be disappointing. As it has been said, “There are no free lunches.” On the other hand, if you want less dependency on all types of glasses and understand that neither distance nor near vision will be perfect, you may be a good candidate for monovision.