Abstract
Purpose:
To compare methodologies of major manufacturers of toric intraocular lenses (tIOL) producing lenses with different amount of astigmatism. Work by our group and others have established that a number of companies use fixed ratio methods for prediction of tIOL implants. As we anticipate an expansion in the range of correction offered with the wide acceptance of tIOL, predictive comparisons are warranted.
Methods:
Based on the spectrum of FDA approved tIOL produced by one company and their fixed toricity ratio as inferred from their online calculator and recent literature and using our validated Universal IOL calculator in constant toricity mode, we generated 120 cases for comparison to the range of astigmatism offered by another company with FDA approved tIOLs in a different astigmatic correction range. These cases covered a wide range of spherical power, mean K and amount of astigmatism.<br />
Results:
Both companies tIOLs predicted a constant amount of residual astigmatism independent of the spherical power of the implant. That amount of astigmatism however differed between the two companies.
Conclusions:
Even among major companies using a fixed toricity ratio method the residual astigmatism differs for the same eye with the same amount of astigmatism and identical power of correction tIOL.