Most people undergoing cataract surgery have an intraocular lens implanted into the eye at the time of the operation, which obviates the need to wear contact lenses after the procedure. However, intraocular lenses don't always correct all visual defects, so some patients need glasses or contact lenses postoperatively.
A cataract occurs when the natural lens within the eye becomes cloudy and interferes with a person's ability to see. When a doctor performs cataract surgery, he removes the natural lens and replaces it with a clear, plastic lens. These intraocular lenses come in several types, including basic lenses, which don't correct any visual defects, and monofocal lenses, which correct either near or distance vision. Doctors often insert a distance-vision lens in the dominant eye and a near-vision lens in the nondominant eye to provide the best postoperative visual acuity. However, this strategy doesn't work for everyone, and many patients still need glasses or contact lenses for performing some tasks.
Premium lenses, such as accommodating lenses and multifocal refractive lenses, correct near, intermediate and distance vision. However, these lenses often cause unwanted effects, such as decreased overall visual acuity, decreased night vision and seeing halos around lights at night.
Doctors choose the best type of intraocular lens for each patient based on a number of factors, including the person's degree of nearsightedness and whether he has an astigmatism, which many intraocular lenses don't correct. The doctor usually reassesses the patient's vision and prescribes appropriate corrective lenses after about one month.