Comparative outcomes of toric intraocular lens (IOL) implantation using ALLY-guided workflow versus ZEISS CALLISTO eye markerless guidance in phacoemulsification cataract surgery: a prospective randomized controlled trial

Precise alignment of toric intraocular lenses is critical for effective correction of corneal astigmatism during cataract surgery, as each degree of postoperative misalignment can reduce astigmatic correction by approximately 3.3percent. This prospective, randomized controlled trial compares the clinical outcomes of toric IOL implantation using two advanced intraoperative guidance systems: the ALLY femtosecond-assisted workflow and the ZEISS CALLISTO eye markerless guidance. The study aims to evaluate refractive accuracy, rotational stability, surgical efficiency, and patient-reported outcomes following phacoemulsification cataract surgery.

Eligible participants are adults with regular corneal astigmatism more than 1.00 D and visually significant cataracts. Subjects are randomized to receive toric IOL alignment via either ALLY or CALLISTO guidance, with standardized preoperative planning, surgical technique, and postoperative care across both arms. The primary endpoint is  proportion of eyes within 0.50 D and 1.00 D of refractive targets, mean absolute residual refractive cylinder at 3 months postoperatively. Secondary endpoints include IOL rotational stability, uncorrected and corrected distance visual acuity, vector analysis of astigmatism (Alpins method), intraoperative metrics, need for IOL repositioning, patient-reported visual quality, and safety outcomes. Outcome assessors are masked to group allocation, and analyses will be conducted on an intention to treat basis with per protocol sensitivity.

This trial will provide high-quality evidence to inform best practices in toric IOL alignment and may influence future adoption of integrated femtosecond platforms versus markerless image guided systems in cataract surgery