Implantation of an Intraocular Lens
Intraocular Lens Options
Most patients undergoing cataract surgery have options regarding the type of IOL to be implanted in their eyes. The choice may depend largely on which type of vision correction will be most convenient for one’s lifestyle. In other cases, co-existing eye conditions limit the effectiveness of certain IOLs, leaving the patient with one clearly best option.
Traditional lens implants have a single curvature and focal point, providing best focusing at a particular distance, such as near vision or far vision. Each patient decides whether to be near-sighted or distance-sighted, and the surgeon chooses lens implants accordingly. For patients who receive implants that maximize distance vision, reading glasses will be used for close tasks, including computer work, reading, and sewing. If IOLs are implanted to make a patient nearsighted, he/she would plan to read without glasses but need spectacle correction for distance tasks, such as driving and watching television.
A number of intraocular lenses with the potential to restore some of the near focusing ability of the eye (accommodation) have been approved by the Food and Drug Administration (FDA,) providing ophthalmologists and their patients with expanded choices for cataract surgery. Depending upon the technological features of the lenses, they are described as “bifocal,” “multifocal,” “accommodating,” “apodized diffractive,” or “presbyopia-correcting.” All of these lenses correct for both distance and some degree of near vision. Your surgeon may determine through the eye examination and a discussion with you that one of these lenses is an appropriate choice for you.
Another option available to cataract patients is “monovision.” In this method, lenses of different powers are placed in your two eyes. The ophthalmologist deliberately corrects one of your eyes for close vision, which would allow you to read without glasses. The fellow eye would receive a distance lens that would provide better far vision. This technique has been employed successfully in many contact lens and implant patients. Your surgeon or staff may discuss and demonstrate this option.
Astigmatism and Toric IOL’s:
Astigmatism is a very common imperfection of the eye and is present when the cornea is not spherical like a basketball. An asymmetrically curved object, such as a football, is said to have a “toric” shape. When a cornea (the front curved surface of the eye) is toric, light rays passing through it do not focus to a single point. The result is “astigmatism” (Greek: not to a point). Glasses and contacts can be made in toric shapes to compensate for the imperfect curvature of the cornea. Likewise, a toric IOL can be implanted instead of spherical one to neutralize astigmatism of the cornea, thereby providing better focusing without glasses than spherical IOLs. In this way, astigmatism can be reduced or eliminated at the time of cataract surgery. If you have a significant degree of astigmatism, this IOL option may be discussed with you.