“An intraocular lens (IOL) is an implanted lens in the eye, usually replacing the existing crystalline lens because it has been clouded over by a cataract, or as a form of refractive surgery to change the eye's optical power. It usually consists of a small plastic lens with plastic side struts, called haptics, to hold the lens in place within the capsular bag inside the eye. IOLs were traditionally made of an inflexible material (PMMA), although this has largely been superseded by the use of flexible materials. Most IOLs fitted today are fixed monofocal lenses matched to distance vision. However, other types are available, such as multifocal IOLs which provide the patient with multiple-focused vision at far and reading distance, and adaptive IOLs which provide the patient with limited visual accommodation.”|
(Wikipedia, Intraocular Lenses, 11/28/2010)

“In general, there are two types of intraocular lenses. One type replaces the eye's natural lens, usually to replace a cataractous lens.  The other type is used to supplement an existing lens and functions as a permanent corrective lens.  This type of lens (referred to as a phakic IOL) is implanted in the anterior or posterior chamber to correct refractive errors of the eye. In theory, the power for either type of IOL required for enmetropia (i.e., point focus on the retina from light originating at infinity) can be precisely calculated.  The power of the implanted lens is selected based on pre-operative measurements of ocular length and corneal curvature to enable the patient to see without or with little vision correction. Unfortunately, due to errors in measurement, variable lens positioning or wound healing, most patients undergoing cataract surgery will not enjoy optimal vision without some form of vision correction following the surgery (Brandser et al., Acta Opthalmol Scand 75:162 165(1997); Oshika et al., J Cataract Refract Surg 24:509 514(1998). Because the power of present IOLs cannot be adjusted post-implantation, the patient typically must use additional corrective lenses such as eye glasses or contact lenses.”
(Knox et al, US Patent 7,789,910, 9/7/2010)

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