By Tina D. Turner, M.D.

Once the natural lens in the eye has been removed, the eye loses its ability to focus light and images clearly on to the retina, the light-sensitive tissue that lines the inside surface of the eye. Before the development of artificial lenses, hard contact lenses or very thick eyeglasses were the only options for correcting vision after cataract surgery.

Artificial Intraocular Lenses

Artificial intraocular (within the eye) lenses were developed in the early part of the 20th century, and Dr. Harold Ridley implanted the first artificial lens in 1949 in London. In 1952, the first artificial lens was implanted in the United States at Wills Eye Hospital in Philadelphia. Since that time, cataract surgery and artificial lenses have continued to evolve and develop.

In most cases, the natural lens is removed and the artificial lens is implanted during the same surgery. The artificial lens is usually placed within the lens capsule, which is the small “sac” or membrane that once enclosed the natural lens and held it in place.

Artificial lenses are made of inert (or non-reactive) materials, such as PMMA, silicone, and acrylic. Just like natural lenses, artificial lenses have refractive power, or the ability to bend light, which helps to focus light rays and images on the retina. Because of this refractive power, it is now possible to correct nearsightedness and farsightedness with artificial lenses.

picture of an artificial intraocular lens
An artificial intraocular lens

Monofocal Lenses

  • At present, monofocal lenses are the type most commonly implanted. Since “mono” means “one,” monofocal lenses provide one type of focused, or clear, vision. They provide clear vision either at distance or near, but not both.
  • Most patients who select monofocal lenses choose to have good distance vision and use reading glasses to help with near visual tasks, such as reading, computer work, or sewing.
  • Some patients, however, may choose to have better near vision and use eyeglasses that will help correct distance vision.
  • Monofocal lenses are typically covered by insurance and Medicare, and usually require no additional out-of-pocket payment.

Astigmatic Lenses

  • Astigmatic lenses (or toric lenses) are monofocal lenses that can correct astigmatism.
  • Because astigmatic lenses can correct astigmatism, they may reduce the need for an astigmatism correction in the patient’s eyeglasses after surgery.
  • Astigmatic lenses are not fully covered by insurance and Medicare, and usually require a substantial out-of-pocket patient contribution.


It is possible, however, to implant a monofocal lens in one eye for distance vision and a monofocal lens in the other eye for reading vision. This technique is called monovision and can provide clear vision at both distance and near after cataract surgery.

Monovision works very well for some patients, while other patients do not tolerate it well. If a patient has used monovision contact lenses in the past, with one eye corrected for distance and the other for near, the same type of monovision can be created with cataract surgery.

If a patient has never experienced monovision, but is interested in learning more, it is recommended that he or she experiment with monovision eyeglasses or contact lenses prior to cataract surgery and determine if monovision is an appropriate solution.

Multifocal Lenses

  • Since “multi” means “more than one,” multifocal lenses provide more than one type of focused, or clear, vision. They attempt to provide clear vision both at distance and near simultaneously.
  • Because multifocal lenses correct both distance and reading vision, they can reduce the patient’s dependence on eyeglasses and contact lenses.
  • Multifocal lenses are not fully covered by insurance and Medicare, and usually require a substantial out-of-pocket patient contribution.

Multifocal lenses can present problems, however. The American Academy of Ophthalmology notes that “…pilots, night drivers, or those who spend a lot of time in front of the computer may not be good candidates for multifocal lenses. Patients who are intolerant of a small amount of glare and/or halos around lights, especially at night, may not be good candidates for these types of lenses.” Also, patients who have significant astigmatism or macular disease should not have multifocal lenses.

You can learn more about artificial lenses at Multifocal Intraocular Lenses: Frequently Asked Questions from the UCLA Laser Refractive Center.