Influence of the use of an intraoperative image-guided alignment system on the refractive outcomes in subjects with preoperative astigmatism: a large comparative retrospective study

BACKGROUND: The aim of this study is to compare the refractive outcomes in a large cohort with preoperative corneal astigmatism who underwent cataract surgery with toric intraocular lens (IOL) implantation assisted (study group) or no (control group) with an intraoperative image-guided cataract planning system (Callisto, Carl Zeiss Meditec, Jena, Germany). METHODS: In this retrospective comparative database study, mean and centroid postoperative cylinder, mean absolute error (MAE) and the proportion of eyes with a prediction error (PE) within ± 0.25 D, ± 0.50 D and ± 1.00 D (both in cylinder and spherical equivalent (SE)) were compared between both groups. These endpoints were also compared depending on the type of preoperative astigmatism, i.e. against the rule (ATR), oblique or with-the-rule (WTR) astigmatism. RESULTS: In total, 31,176 cases were analyzed in this study. Mean (± standard deviation (SD)) postoperative cylinder was found to be significantly lower in the study group (0.419 ± 0.432 D) compared with the control group (0.443 ± 0.453 D, p < 0.001). This statistical difference was observed in eyes with ATR and oblique astigmatism when looking at subgroups. Postoperative centroid cylinder (mean @angle ± SD) was 0.042 @97° ± 0.600 D in the study group and 0.043 @100° ± 0.633 D in the control group. MAE in cylinder was significantly lower in the study group compared to the control group. A slight but significantly higher percentages (up to 3%) of eyes with a PE in cylinder within ± 0.25 D, ± 0.50 D and 1.00 D were observed in the study group compared to the control group. CONCLUSIONS: Results of this study showed that the use of CALLISTO surgical planning system can improve refractive outcomes after cataract surgery and toric IOL implantation in patients with preoperative corneal astigmatism, especially in terms of cylinder for ATR and oblique astigmatism.