Influence of angle Kappa on the optimal intraocular orientation of asymmetric multifocal intraocular lenses

Abstract

Purpose to evaluate the effects of kappa angle and intraocular orientation on the theoretical performance of asymmetric multifocal intraocular lenses (MIOL). Methods For a total of 21 corneal aberrations, a computational analysis simulated the implantation of a computationally designed MIOL. An image quality parameter (IQ) (visually modulated transfer function metric) was calculated for a 5.0-mm pupil and for three conditions: distance, intermediate, and near vision. The procedure was repeated for each eye after a rotation of the MIOL with respect to the cornea from 0º to 360º in 5º steps. Kappa angles from 0 to 900 microns, in 150 microns steps, combined with two two variants of MIOL centration were tested: in the corneal apex or in the center of the entrance pupil. A p-value ≤ 0.05 was considered significant. Results There were statistically significant differences of the IQ depending of the intraocular orientation of the MIOL. If kappa angle was increased, there was a statistically significant decrease of the IQ. The IQ maintained stable when the optimal intraocular orientation was re-calculated for each kappa angle. In general, the inter-variability of the results between subjects was very high. There were no strong evidences supporting that there exists a preferable centration point. Conclusions Our results suggest that kappa angle theoretically affects significantly the performance of asymmetric MIOL implantation. However, its negative effect can be compensated if a customized intraocular orientation is calculated taking into account the presence of the kappa angle.

The Influence of Angle Alpha, Angle Kappa, and Optical Aberrations on Visual Outcomes after the Implantation of a High-Addition Trifocal IOL

“…Although there has been an increasing interest in clarifying the possible predictive value of optical aberrations, angle kappa, and angle alpha in patient selection prior to MIOL implantation, only limited scientific evidence is available. The published results are sometimes contradictory or provide only moderately strong evidence [1,2,7,9,[11][12][13]19,20,23,24]. Additionally, the definition of angle kappa and alpha are not always the same in the literature, and measurement techniques often vary in different studies [25].…”

Outcomes of a Refractive Segmented Bifocal Intraocular Lens with a Lower Near Addition

“…Consideration of angle kappa in asymmetric segmented bifocal IOLs is a frequently discussed topic. [22][23][24] Yet, customized angle kappa implantation showed little impact on outcomes of the SBL-3 IOL, 25 the predecessor of the IOL evaluated in the current study. However, another small study found that pupil size might be of some relevance for this type of intraocular lens, and these findings deserve further investigation.…”

Katy kappa i alfa w diagnostyce przedoperacyjnej pacjentów nadwzrocznych kwalifikowanych do wszczepienia soczewki wieloogniskowej z uzyciem technologii iTrace

“…Preoperative and postoperative quality of vision is a parameter that is rarely evaluated today, and the focus is placed mainly on the evaluation of visual acuity. The documented influence of the value of the above angles on vision has been the subject of many articles and confirms their indisputable importance in the process of qualification for implantation of premium class lenses, both concentric and asymmetric in their structure [1][2][3]. The evaluation of HOA generated by the cornea is one of the stable elements of qualification for surgery using a premium class lens [4].…”