Mini Review Posterior Corneal Astigmatism and It’s Importance in Selection of Toric Intraocular Lens

This mini review focuses on the current knowledge on posterior corneal astigmatism based on the latest research. In the first part the definition, the magnitude as well as methods and devices for its evaluation are presented. Posterior corneal astigmatism measurement is improving as new technologies are evolving. It is now shown that the posterior corneal surface acts as a negative lens and as a result the total corneal power is overestimated in eyes with the rule anterior astigmatism and underestimated in eyes with against the rule when only the anterior corneal surface is taken in account. In the second part emphasis is given to the effect of posterior corneal astigmatism on toric intraocular lens calculations. The available nomograms and formulae that can be used and their accuracy are discussed. Finally the steps needed to be taken for the best possible result when calculating toric intraocular lenses are presented.