Comparison Of Toric Axis Alignment Accuracy Between Catalys Femtosecond Laser (Cos 7 Premium) And Callisto System In Cataract Surgery

Accurate toric intraocular lens (IOL) alignment is essential for achieving optimal astigmatism correction in cataract surgery. The Zeiss Callisto Eye uses intraoperative digital overlays based on scleral vessel tracking for toric alignment, while the Catalys Femtosecond Laser (Cos 7 Premium) uses iris registration to create corneal laser marks to guide positioning. Although both systems aim to improve alignment accuracy, direct comparative data between these methods remain limited. The purpose of this study is to compare the toric axis alignment accuracy of the Catalys femtosecond laser (Cos 7 Premium) and the Callisto system in patients undergoing cataract surgery with toric IOL implantation.

This retrospective study included patients who underwent laser-assisted cataract surgery with toric IOL implantation at Yitzhak Shamir Medical Center, Israel.

Twenty patients underwent cataract surgery with toric IOL implantation using both the Zeiss Callisto Eye and the Catalys Femtosecond Laser. The axis as was marked on the cornea by the Catalys system using Iris registration was compared to the Callisto axis. Surgeries were recorded, and intraoperative axis alignment was analyzed from the surgical videos. The primary outcome was the mean absolute difference between the Callisto target axis and the Catalys axis. Secondary outcomes included the proportion of cases within ±2°, ±5°, and ±10° of the target axis.

A total of 20 patients (11 men, 9 women, mean age 71.2 years) were included.  In 2 cases, the Catalys femtosecond laser failed to recognize the iris registration, preventing corneal mark placement.  The mean absolute difference between the Callisto axis and the Catalys corneal marks was 1.02° ± 1.24° (SD). The maximum difference observed was 4.4°. 77.8% of cases showed alignment within ±2°, while 100% were within ±5°.

Both the Callisto Eye and Catalys femtosecond laser provided reliable intraoperative toric alignment. However, while most cases showed minimal deviation, some had larger discrepancies. Further studies with larger cohorts are needed to determine their impact on postoperative outcomes.