Comparison of two digital alignment systems for toric intraocular lens implantation.

PURPOSE To compare the two most used digital alignment systems regarding precision, repeatability and loss of track. METHODS 15 eyes of 15 patients older than 21 years with cataracts were included in this prospective study. The two systems were intraoperatively superimposed and recorded, and the alignment of the two displayed alignment axes was analysed regarding precision, repeatability and loss of track. RESULTS There was a significant difference in precision and repeatability between the two digital alignment systems regarding the projected alignment axis. The deviation from the actual target axis was significantly different, with a mean of 0.34°±0.75° for the Zeiss system and 1.60°±1.08° for the Alcon system (p=0.03, n=14). The within-subject SD was significantly lower with 0.21° for the Zeiss system and 0.34° for the Alcon system (p=0.03, n=14). CONCLUSIONS The Zeiss Callisto system showed a significantly lower deviation from the target axis, higher stability with eye movements and less need for microscope illumination than the Alcon system. Both systems showed high precision when compared with manual marking methods. TRIAL REGISTRATION NUMBER NCT05220683.