Accuracy and precision of a new system for measuring toric intraocular lens axis rotation

We determined the accuracy and precision of a new system for measuring postoperative toric intraocular lens (IOL) axis rotation. The system performs high-resolution retroillumination photography to identify toric IOL axis markings and then takes a photograph of the iris and conjunctival/scleral vessels. Built-in software measures the toric axis to within 0.2 degree. If performed twice on the same eye, the system will correct the 2 toric axis measurements for cyclorotation/head tilt using iris/vessel registration. Testing in 37 eyes showed that using iris/vessel registration correction reduced the mean absolute toric IOL axis rotation by a factor of 4.5. We conclude that this system seems to be both accurate and precise for measuring postoperative toric IOL axis rotation.