[Aspheric intraocular lenses].

BACKGROUND: Over the last years, the implantation of intraocular lenses (IOLs) has become a safe, effective, stable, and well-predictable procedure of lens replacement surgery. Therefore, manufacturers and surgeons have given special attention to the optical quality these lenses can achieve. Because spherical aberration of the natural lens changes in life from negative to positive values and hence impairs optical quality, implanting an aspheric IOL based on the young natural lenses' asphericity parameters, inducing negative, neutral, or individual spherical aberration, should improve the optical quality. Parameters used to evaluate optical quality are visual acuity, contrast sensitivity, glare disability, night vision, higher-order aberrations, and subjective questionnaires.
METHOD: This article provides a survey of different kinds and principles of aspheric IOLs, current trials, and criteria used to estimate lens benefits.
RESULTS: Benefits of aspheric lenses have been shown in several studies. However, adjustment of the cornea's positive spherical aberration by an aspheric IOL can be demonstrated only in larger pupils. For young patients with distinctly larger mesopic and scotopic pupils who undergo refractive lens exchange, aspheric IOLs should be implanted. As higher-order and lower-order aberrations of the eye interact with each other, this fact will have to be taken into consideration when correcting spherical aberration. Spherical aberrations differ interindividually; therefore, individualisation of asphericity may be useful, either by choosing different IOLs depending on the eye's spherical aberration or by individual IOL surface design.
CONCLUSION: The use of aspheric IOLs for lens replacement reduces spherical aberration and therefore improves the optical quality of the eye.