Minimising residual aberration in the presence of cyclotorsion uncertainty in refractive surgery

PURPOSE: To formulate a simple valid method to minimize the residual aberration magnitudes due to uncertainty in cyclotorsion measurement. SETTING: Optics research laboratory. METHODS: Assuming that cyclotorsion error can be estimated and compensated for with a certain level of uncertainty, we formulate a function to modify the wavefront error in order to minimize the residual aberration magnitudes due to cyclotorsion measurement uncertainty. A modal optimum nomogram factor is computed for minimization of the residual aberration for each Zernike mode. We also calculate the optimized residual aberration using the minimization factor. RESULTS: For modal optimum, the minimization factor was dependent only on Zernike meridional order and cyclotorsion uncertainty. Th e value of the minimization function ranged between –1 and +1. CONCLUSION: In a perfectly performing system, an " overplanned " treatment will never minimize residual wavefront aberration, independent of the cyclotorsion uncertainty. An " underplanned " treatment calculated using the presented approach will minimize the residual aberration magnitude imposed by the higher order Zernike terms, and will reduce its relative orientation to the original aberration pattern. Th e gains using this method are undeniably modest, but at such low implementation costs can still be valuable.