Predictability of residual astigmatism after implantation of posterior chamber toric lenses

The objective of the study was to examine the predictability of residual astigmatism after cataract surgery and implantation of the posterior chamber aspheric toric lens TECNISA (R) ZCT, Abott Medical Optic (Ettlingen, Deutschland). The retrospective study included a total of 88 patient eyes undergoing a cataract operation with a toric lens implantation between March 2014 and October 2015. The inclusion criteria were a regular astigmatism of at least 0.75 dpt. Posterior chamber toric lenses (model Tecnis ZCT) were exclusively implanted. Post-surgery check-ups were performed after 1 day, 1 month and 2 months. Main study outcome was best-corrected visual acuity (BCVA), spherical and astigmatic aberration and the difference between expected and actual residual astigmatism after cataract surgery. The median reduction of corneal astigmatism was from -2.50 dpt (+/- 1.06 dpt) to -0.75 dpt (+/- 0.51 dpt) (p <= 0.05). The median BCVA increased from 0.37 logMAR (+/- 0.25 logMAR) before surgery to 0.09 logMAR (+/- 0.10 logMAR) after surgery. The spherical equivalent was reduced from +3.50 dpt (+/- 1.11 dpt) (presurgery) to -0.56 dpt (+/- 0.51 dpt) (postsurgery) in hyperopic patients and from -2.44 dpt (+/- 3.03 dpt) to -0.69 dpt (+/- 0.81 dpt) in myopic patients. By using the power vector analysis no significant deviation from the expected target values was observed; however, the median discrepancy between the expected and actual residual astigmatism was -0.50 dpt despite a surgical orientation of the intraocular lens (IOL) within 5A degrees of the desired axis. The IOL showed a median rotation of 3.00A degrees (+/- 4.46A degrees). Implantation of the aspheric toric intraocular lens Tecnis ZCT is a predictable, effective and reproducible tool in cataract surgery to account for regular corneal astigmatis; however, despite an optimal surgical orientation of the toric IOL, a small and rarely a large discrepancy might occur between expected and actual residual astigmatism.