The effect of lateral and torsional misalignments of the ablation on the postoperative optical outcome was theoretically investigated based on measured wavefront aberration data from 130 normal eyes. Simulations included lateral decentrations and rotations around the longitudinal axis of the eye (torsion). The optical quality of the simulated refractive correction was rated by means of the root-mean-squared residual wavefront error. The accuracy for lateral centration in order to achieve the diffraction limit at a pupil size of 8 mm in 95% of the investigated eyes should be 50 microns or better. However, an accuracy of 450 microns was found to be enough to guarantee that none of the investigated eyes would suffer from a decreased optical performance after surgery. Alignment would have to be performed with a torsional precision of approximately 1 deg or better in order to achieve the diffraction limit in 95% of the measured normal eyes for an 8-mm pupil, whereas an accuracy of 15 deg is required to obtain at least some improvement of the optical quality in all the examined eyes. The accuracy needed for torsional alignment increases compared to pure sphero-cylindrical treatments when additional correction of the higher-order aberrations is aspired.

Date Published: 13 June 2002
PDF: 12 pages
Proc. SPIE 4611, Ophthalmic Technologies XII, (13 June 2002); doi: 10.1117/12.470594

Published in SPIE Proceedings Vol. 4611:
Ophthalmic Technologies XII
Fabrice Manns; Per G. Soederberg; Arthur Ho, Editor(s)