Rotational stability of a single-piece hydrophobic acrylic intraocular lens: New method for high-precision rotation control

To use a new method to examine precisely the rotational stability of a foldable hydrophobic single-piece monofocal acrylic intraocular lens (IOL) and determine whether the design is suitable for a toric lens.University Eye Hospital, University Giessen and Marburg, Giessen, Germany.The rotational stability of an acrylic IOL (AcrySof SA60AT, Alcon) was evaluated using digital photographs. Two sets of images of the IOL in 17 eyes were taken. The first set was taken immediately postoperatively and the other, 6 months after cataract surgery. The axial position of the eye was determined using 2 characteristic points at the conjunctiva and on the IOL. These points were then connected with a line and an angle determined. Comparing the 2 sets of images yielded an angle Delta that revealed the rotation.The median IOL rotation was 0.7 degree (range 0.1 to 1.8 degrees). Rotation greater than 0 degree and less than 0.5 degree was measured in 4 eyes (24%). Rotation of 0.5 to 1.0 degree was found in 8 eyes (47%). A rotational angle greater than 1.0 degree was found in 5 eyes (29%). Rotation did not exceed 1.8 degrees in any eye.Using a suitable measuring method that takes into account the cyclorotation of the eye, it was possible to precisely determine IOL rotation using picture pairs taken in chronological sequence. The IOL design examined in the study is recommended as a toric IOL because of its good rotational stability.