Changes in Refraction Induced by Change in Intraocular Lens Position

Abstract

BACKGROUND: Intraocular lens (IOL) deceleration and tilt may affect postoperative refractive errors through spherical aberration of the IOL. METHODS: Through a use of a ray-tracing program and by minimizing algorithm, we calculated theoretical refractive errors for various degrees of IOL decentration and tilt. We compared our results with those obtained by paraxial vergence calculations. RESULTS: IOL decentration and/or tilt shifted postoperative refractive errors toward myopia and astigmatism of oblique origin. For example, a 3millimeter decentration of an IOL resulted in induction of approximately - 2.00 diopters (D) sphere and + 0.70 D cylinder. IOL tilt affected refractive errors to a lesser degree. The change in refractive error caused by a combination of IOL decentration and tilt depended on the relationship between the geometrical axes of decentration and tilt. In the case of the least favorable combination of 12° of tilt and 3 mm of decentration, it can reach - 7.00 D sphere and + 4.00 D cylinder. CONCLUSIONS: IOL decentration and/or tilt increase myopia and astigmatism. They are negligible for small decentrations, but could be sources of substantial postoperative refractive errors if the decentration or tilt is large. [J Refract Corneal Surg. 1994;10:556-564.] RESUME INTRODUCTION: La decentration et l'inclinaison de la lentille intra-oculaire (LIO) ont des effets sur la réfraction post-opératoire à cause de l'aberration sphérique. METHODES: En utilisant un programme à rayons dessinés et un algorithme minimisant nous avons calculé les erreurs réfractives correspondants aux plusieurs décentrations et inclinaisons des LIO. Nous avons comparé les résultats avec ceux des calculs de vergence paraxialle. RESULTATS: La decentration et l'inclinaison des lentilles intra-oculaires changent l'erreur refractive vers la myopie et l'astigmatisme oblique. Par example, une decentration de 3 mm entraîne un changement de -2.0 D sphérique et +0.7 D cylindrique. L'inclinaison des LIO a moins d'effet. Le changement dans l'erreur refractive entraîné par la combinaison d'une decentration et d'une inclinaison d'une LIO dépend du rapport entre les axes de la decentration et de l'inclinaison. Le changement peut atteindre -7.0 D pour le sphérique et +4.0 D pour le cylindrique dans la pire combinaison 12 degrés d'inclinaison et 3 mm de decentration. CONCLUSION: La decentration et l'inclinaison des LIO augmentent la myopie et l'astigmatisme. Elles ont peu d'effets dans les petites positions mauvaises, mais entraînent des erreurs réfractives significatives quand la decentration ou l'inclinaison est plus grande. (Translated by Robert Mack, MD, Kansas City, Mo.) SOMMARIO PREMESSA: Il decentramento e l'obliquità delle lenti intraoculari (IOL) generalmente compromettono, a causa delle aberrazioni sferiche della IOL, la refrazione postoperatoria. METODI: Utilizzando un programma di tracciamento dei raggi e minimizzando l'algoritmo, abbiamo calcolato gli errori refrattivi teorici per vari gradi di decentramento ed obliquità delle IOL. I nostri dati sono stati confrontati con quelli ottenuti tramite il calcolo della vergenza para assiale.

A Modified Knotless Transscleral Intraocular Lens Fixation Technology for Congenital Ectopia Lentis

“…In contrast, the traditional method requires two sides of the suture to be fixed and knotted in turn, which is not conducive to allowing correction of the IOL position and the probability of IOL tilt was greater. Previous study confirmed that IOL tilt can cause postoperative intraocular astigmatism and influence the refractive error [ 24 ], the smaller astigmatism with the modified knotless method may be explained by smaller IOL tilt [ 25 ], whereas the smaller IOL tilt was associated with the operation procedures and technique, especially the knotless Z-suture.…”

Predictability of pseudophakic refraction using patient-customized paraxial eye models

“…Other factors contributing to prediction error include potential tilt and decentration of the IOL. 30,31 In the paraxial model, we assumed that the IOL is aligned and centered relative to the A-line passing through the corneal apex. Certainly, the IOL position after implantation has varying degrees of decentration and tilt.…”

Evaluation of Intraocular Lens Tilt and Decentration in Congenital Ectopia Lentis by the Pentacam Scheimpflug System

“…As previous studies have shown, IOL decentration greater than 0.4 mm and tilt greater than 7 °could induce a lower visual performance [9]. Korynta found that an IOL tilt of 12 °and decentration of 3 mm could result in a postoperative myopia of −7.0D and astigmatism of +4.0D [10]. Hence, the position of the IOL is important for a good visual prognosis.…”