A review of angle kappa and multifocal intraocular lenses and their effect on visual outcomes.

Although most patients are satisfied with their vision after multifocal intraocular lens (IOL) implantation, dissatisfaction has been reported for various reasons, including poor visual outcomes and visual disturbances. Many published reports hypothesise that preoperative angle kappa may be an associated factor in patient dissatisfaction. Therefore, there is considerable interest in understanding the connection between preoperative angle kappa and visual outcome after multifocal IOL implantation. This narrative review presents clinical data on angle kappa and its relationship to visual outcomes, visual quality, IOL position and visual disturbances after cataract surgery and multifocal IOL implantation. Although recent advances improved objective measurement of angle kappa, inconsistencies in reporting angle kappa make comparison across studies and patient populations difficult. The consensus among multiple studies was that angle kappa did not influence visual and refractive outcomes following multifocal IOL surgery. However, there were conflicting reports on the correlation between angle kappa and subjective visual quality and patient-reported visual disturbances. Differences in study design, patient characteristics and multifocal IOL characteristics may explain these discrepancies. IOL orientation, tilt and decentration may be affected by angle kappa and likely contribute to some visual disturbances. Additional modelling studies using multifocal IOLs and ocular biometry could improve our understanding of the relationship between angle kappa and IOL alignment. Accurate assessment of preoperative angle kappa in patients with cataracts is important for successful outcomes and patient satisfaction.