To determine the accuracy of two axis-marking methods for toric intraocular lens (IOL) implantation, one picture-assisted approach based on scleral vessel vectors, and the other based on a self-leveling device for manual marking.

This retrospective single-center study involved 60 eyes of 51 participants, who underwent phacoemulsification with toric IOL implantation. In all eyes, preoperative markings were made in a seated position both manually via a self-leveling corneal marker (RoboMarker), and digitally on slit-lamp photographs, defining scleral vessels as landmarks, aiding to find the correct intraoperative orientation for an angular graduation instrument. The axis of IOL alignment at the end of surgery was determined from high resolution, intraoperative footage from a microscope-integrated camera and the axis-marking error served as an outcome measurement for both marking techniques. The endpoint was the alignment of the lens at the end of surgery.

The average axis-marking error was 2.5 ± 1.9 degrees for picture-assisted marking, which was significantly less than that of the self-leveling corneal marker, being 5.4 ± 4.4 degrees.

Our results indicate that scleral vessel vector marking leads to highly accurate toric IOL alignments, while being an inexpensive technique, as solely a slit-lamp camera is required for preoperative preparation.