Abstract
Purpose :
Accurate alignment of arcuit incisions for the treatment of corneal astigmatism is complicated by rotations of the patient’s eye between pre-operative measurements and the position of the patient’s eye while docked to the treating laser system, however, the magnitude and source of such rotations is uncertain. To determine the magnitude of rotation of the patient’s eye during femto-second cataract procedures, we measured the rotation of subject eyes via registration of iris features in three conditions; pre-operative upright corneal measurements, supine corneal measurements at the laser system prior to docking, and fully docked to the laser system.
Methods :
Thirty volunteer subjects were enrolled for the study. The subject’s corneal astigmatism was measured along with capturing a simultaneous iris image using the iDesign and a Catalys system modified to measure corneal astigmatism and capture simultaneous iris images in the supine position prior to docking. An additional iris image was captured while docked to the Catalys system. The rotational position of the subject eyes was measured by two graders and averaged by locating the same iris features in all three iris images for each subject. The subject eyes were dilated for both measurements with the Catalys system, but not dilated for the iDesign measurements. The rotational difference between the iDesign images and the Catalys astigmatism images was noted as “cyclorotation”. The rotational difference between the Catalys astigmatism images and Catalys docked images was noted as “docking induced rotation”.
Results :
Twenty-four (24) eyes of subjects were successfully imaged in all three conditions. The age range was 28yrs to 63yrs. There were 16 males, 8 females, 9 eyes OD, and 15 eyes OS. The range of measured cyclorotation was 10.8°(max.9.3°, min.-1.5°, σ=2.8° ). The range of measured docking induced rotation was 25.2°(max.12.6° min. -12.7°, σ=6.6°).
Conclusions :
The rotation of a patient’s eye induced in the docking process is significantly larger than cyclorotation. The combined effect of cyclorotation and docking induced rotation, at an uncertainty level of three standard deviations, is likely to be in the range of +/-22°.
© Johnson & Johnson Surgical Vision, Inc.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.