How to calculate surgically induced astigmatism after cataract surgery?

Corneal astigmatism is a complex entity with a power and an axis. The purpose of this article is to give a summary of the most popular methods to calculate surgically induced astigmatism, and to discuss their differences. Various methods exist, but we will only discuss the most popular ones. The interested surgeon can use these methods on his patients to calculate and compare the surgically induced astigmatism of each of his surgical techniques. Doing so, he will be able to use the ideal technique in each individual case. Astigmatism-neutral as well as astigmatism-inducing techniques should be used. A correct pre- and postoperative keratometry is of course very important.