Effects of intraocular lens position errors on postoperative refractive error.

Previous theoretical attempts to predict the refractive effects of intraocular lens (IOL) misalignment have resulted in conflicting information. Discrepancies in both the potential magnitude and direction of the refractive changes exist in the literature. This paper provides a detailed description of the mathematical framework required to achieve a valid predictive model and a quantitative analysis of the effects of IOL positional errors. The effects of misalignment are shown to influence the spherical refractive component primarily. Astigmatism related to oblique incidence is generally small. Movement of the IOL away from the retina produces myopia, while movement toward the retina produces hyperopia. It is likely that longitudinal IOL positional errors are a principal component of postoperative refractive errors. Alignment errors, on the other hand, must have generally minor effects on refraction.