To compare the error in predicted residual astigmatism using an Integrated mean or median K from multiple instruments using the Barrett K calculator.
The preop keratometry, post op refraction and meridian of the implanted IOL were measured in a series of 128 patients who had cataract surgery performed with a toric intraocular lens. Using vector calculations, the error in predicted residual astigmatism was compared using an Integrated K or the K from single instruments
With a single instrument, the percentage of cases with a predicted error in residual astigmatism of 0.5 D or less ranged from 60.2% to 71.8%. Using the median integrated K from two biometers (Lenstar and IOLMaster 500) and a topographer (Pentacam) the percentage of cases within 0.5 D of predicted error in residual astigmatism improved to 78.1%. The predicted error in spherical equivalent refraction, however, was similar whether an integrated K or K from a single instrument was used to predict the spherical IOL power.
Calculating a mean or median K from multiple instruments is an objective method which significantly improves the prediction of residual astigmatism.