To analyze the change in posterior corneal astigmatism and total corneal astigmatism in patients with anterior corneal astigmatism less than 1.0 diopter (D).

In the present study we evaluated 52 eyes with anterior corneal astigmatism less than 1.0 D. Patients were divided into 2 groups according to steep axis: Group 1 included 33 eyes with within-the-rule (WTR) astigmatism and Group 2 included 19 eyes with against-the-rule (ATR) astigmatism. Anterior, posterior and total corneal astigmatism were measured using Scheimpflug imaging (Pentacam®).

In Group 1, preoperative anterior astigmatism, posterior astigmatism and total astigmatism were 0.55 ± 0.44 D, 0.31 ± 0.14 D and 0.30 ± 0.72 D, respectively. At postoperative 2 months, anterior astigmatism, posterior astigmatism and total astigmatism were 0.51 ± 0.67 D, 0.31 ± 0.15 D and 0.35 ± 0.81 D, respectively. There was no statistically significant difference between preoperative and postoperative anterior, posterior and total corneal astigmatism in Group 1. In Group 2, preoperative anterior astigmatism, posterior astigmatism and total astigmatism were -0.48 ± 0.46 D, 0.26 ± 0.09 D and -0.51 ± 0.65 D, respectively. At postoperative 2 months, anterior astigmatism, posterior astigmatism and total astigmatism were -0.17 ± 0.68 D, 0.25 ± 0.13 D and -0.30 ± 0.55 D, respectively. There was no statistically significant difference between preoperative and postoperative anterior, posterior and total corneal astigmatism in the 2 groups. There was no statistical correlation between preoperative posterior corneal astigmatism and postoperative 2 months total corneal astigmatism. After vector analysis, surgically induced astigmatism (SIA) of the anterior and total astigmatism in Group 1 were 0.03 D @ 30° and 0.07 D @ 74°, respectively, and in Group 2 were 0.27 D @ 100° and 0.36 D @ 86°, respectively.

In patients with preoperative total corneal astigmatism less than 1.0 D, posterior corneal astigmatism had a small effect on postoperative total corneal astigmatism.