Intraocular lens tilt and decentration measurements: Purkinje imaging versus Scheimpflug imaging

Purpose: To measure tilt and decentration of intraocular lenses (IOLs) with Scheimpflug and Purkinje imaging systems. Methods: Measurements of IOL tilt and decentration were obtained using a commercial Scheimpflug system (Pentacam, Oculus) and custom algorithms, and a custom-built Purkinje imaging apparatus. Both methods were validated with a physical model eye where tilt and decentration can be set nominally. Twenty-one eyes of 12 patients with IOL implanted were measured with both systems. Results: Slopes and correlation coefficients of measurements on the physical model eye showed an absolute discrepancy between nominal and measured values of 0.279 deg (Purkinje) and 0.243 deg (Scheimpflug) for tilt and 0.094 mm (Purkinje) and 0.228 mm (Scheimpflug) for decentration. In patients, we found an average tilt less than 2.6 deg and average decentration less than 0.4 mm. We found mirror symmetry between right and left eyes for tilt around vertical axis and for decentration in the horizontal axis, as revealed by both techniques. Conclusions: Both systems show a high reproducibility. Validation experiments on physical model eyes shows slightly higher accuracy with the Purkinje than the Scheimpflug imaging method. Horizontal measurements on patients from both techniques are highly correlated. IOLs tend to be tilted and decentered nasally in most patients. Intraocular lens tilt and decentration from Purkinje and Scheimpflug imaging