The importance of angle kappa for centration of multifocal intraocular lenses

Abstract To evaluate patient satisfaction with multifocal intraocular lens (MIOL) implants (AcrySof Restor) in relation to the size of angle kappa and precise centration of the MIOL. Fifty-two eyes of 26 patients were included in this study. All patients underwent bilateral phacoemulsification and multifocal intraocular lens implantation (AcrySof Restor) from January 2008 to April 2010. Preoperative and postoperative examinations included slit lamp biomicroscopy, near and distance uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity and measurement of angle kappa. Precise centration of the IOL with respect to the centre of the pupil was evaluated postoperatively. Subjective photic phenomena were evaluated separately for each eye and the patients were asked to compare the perception between the right and left eye. Angle kappa was positive in all cases, ranging from +1° to +7°. The mean angle kappa was 2.78° and 2.10° in the right and left eye, respectively. The IOL was centred exactly to the centre of the pupil in 40 eyes. In twelve eyes there was a slight decentration of the IOL (3 nasal, 4 temporal, 2 superotemporal, 2 superior, 1 inferior). Different subjective perception of photic phenomena between the two eyes was recorded only in five patients. All these patients were among those with a decentred IOL. Temporal and superotemporal decentration of the IOL caused pronounced photic phenomena in five cases - in four cases there was a greater angle kappa of +3° to +4°. In one case of temporal decentration and a small angle kappa (+1°), the patient failed to observe a difference between both eyes. In the cases of inferior, superior and nasal decentration of the IOL, no difference between both eyes was seen. According to our results, temporal decentration of the IOL is associated with the greatest risk in multifocal IOL implantation, particularly in cases with a higher angle kappa. An evaluation of angle kappa should be a part of preoperative examination before MIOL implantation. Patients with a high angle kappa should be excluded because of a higher risk of postoperative photic phenomena. Key words: angle kappa, multifocal intraocular lens, photic phenomena.