Astigmatism of the Cornea

Total corneal astigmatism is determined by both the anterior and posterior corneal surfaces. Ignoring posterior corneal astigmatism may yield an incorrect estimation of total corneal astigmatism. Correcting corneal astigmatism based on only anterior corneal measurements could lead to overcorrection in eyes that have WTR astigmatism and undercorrection in eyes that have ATR astigmatism. The ATR change that occurs with aging should be taken into consideration at the time of cataract surgery. Devices with more accurate and repeatable anterior and posterior corneal measurements are desirable.