Name

Surcorrection optimale pour implants toriques en chirurgie de la cataracte

Until recently the correction of astigmatism by toric IOLs used a strategy of consistently undercorrecting the target astigmatism with the available discrete choice of tIOL.   Several arguments were advanced for such a choice.    More recently a trend has developed to "split the difference" and over or under correct according to minimizing the absolute value of the residual astigmatism, with minimal consideration to the slightly preferable with the rule residual.

The methodologies are analyzed and specific tIOL calculators and algorithms examined across methodologies and manufacturers to characterize "the lay of the land" and the key contributions are reviewed.   A rigorous analysis is then carried out based on the analysis of all sources of both the mismatch and misalignment of toric IOLs and their consequences for the final expected residual astigmatism.

The analysis described yields a very specific, non-intuitive algorithm that is consistent neither with the "always undercorrect", nor the "split the difference" approach.   The algorithm is demonstrated to be optimal and several examples spanning the spectrum of SIAs and low to very high astigmatism are presented and demonstrate the consistency and the optimality of the presented method.

The current status of the decision making for the choice of a tIOL is far from ideal resulting in suboptimal refractive results.  In our neverending quest towards perfect refractive result the specific question of when is it best to overcorrect astigmatism needs addressed formally, rigorously and in a manner consistent with our surgical environemnt and our patient needs and best interest.  We present such an approach and its exact results.

An optimal solution for the decision of when to overcorrect ("flip the axis") is presented and demonstrated rigorously, then illustrated with a broad spectrum of surgical cases.