Presbyopia: A big word that means if your distance prescription is fully corrected, you will need bifocals or reading glasses around age 40.
Presbyopia is an unavoidable and frustrating fact of life. It is caused by the normal aging process and is mostly due to the natural lens in your eye becoming less able to change shapes, or accomodate. If you give a young eye a near target, the natural lens in the eye will automatically fatten, creating magnification to move the focal point on to the near target. The same eye, will naturally relax, allowing the lens to lengthen or flatten, when the focal point moves to a distance target. the process of losing accomodation starts around age 40 and continues to worsen until around age 65, at which time no accomodation remains.
Some of you may be thinking about someone you know who is older than 40, and sees well both at distance and near without glasses (or contacts). This is possible if one eye has a naturally low near-sighted refractive error (or prescription) such as -2.00. If you do not correct that distance refractive error, you essentially have two units of magnification for clear near vision. This eye will be blurry in the distance, and clear at near. If this same person is lucky enough to have a good uncorrected distance vision in the other eye, they have monovision. This means one eye is set for good near vision and one is set for good distance vision. Many people enjoy monovision because it allows them to avoid needing reading glasses for most tasks. Monovision can be created fairly easily with contact lenses in one or both eyes. Regardless of the refractive erroe in each eye, If contacts can set one eye for distance and one for near, the patient should be able to see failry well at a distance. (Example: if a patient is -4.00 in easch eye, then this patient should wear -4.00 in one eye and -2.00 in the other eye.)
We have learned that is a patient likes monovision in contact lenses, they may also enjoy monovision after cataract surgery. The implant that replaces the cloudy natural lens, or cataract, come in various powers, much like contact lenses. Your cataract surgeon can use a computer program to predict each eye’s post-operative results, and select the implant power according to how tha patient wants to see after surgery. It is common for a patient to achieve good overall vision without the need for glasses following cataract surgery if one eye is set for distance (basically no power neede) and one eye set for near (approximately -2.00)