APR 23, 2008
This theoretical analysis used keratometric data from 806 corneas to demonstrate that considering surgically induced astigmatism (SIA) when implanting toric intraocular lenses (IOLs) can significantly improve IOL selection ability.
Eyes included in the study had preoperative corneal astigmatism of 2.50 diopters or less. The study's author provided a clear explanation of why the amount of astigmatism to be corrected at the time of surgery must be the vector sum of the preoperative corneal astigmatism and any SIA.
The AcrySof Toric IOL Calculator (Alcon Laboratories, Inc., Hünenberg, Switzerland) simplifies the process of considering SIA when selecting an IOL. The calculator, which was used by the author in conducting the study, determines the optimal AcrySof IOL based on the manufacturer's recommendations by incorporating a default expected SIA or a surgeon's known SIA for either a temporal or superior incision, since incision type can affect SIA. Even a nominal amount of SIA of 0.50 D will affect surgical results and the selection of an appropriate IOL, the study's results indicated.
Dr. Singer has received lecture fees from Eyeonics, Inc., and Carl Zeiss Meditec. Dr. Singer is an equity owner in Eyeonics.