To assess the changes in anterior, posterior, and total corneal astigmatism after cataract surgery with on-axis clear corneal incision cataract surgery.

This study included 48 eyes (24 eyes with 'with-the-rule [WTR]' and 24 eyes with 'against-the-rule [ATR]') that underwent phacoemulsification and intraocular lens insertion through on-axis clear corneal incision. The ATR group with vertically steep axis of posterior corneal astigmatism was divided into subgroups 1 and 2 for the opposite axis. Autorefraction, uncorrected and best-corrected visual acuities were measured. Corneal astigmatism (anterior, posterior and total) was measured using Pentacam® preoperatively and 1 week, 1 month, and 2 months postoperatively.

Multivariate linear regression analysis of preoperative data showed positive correlations among anterior, posterior and total astigmatism. Anterior corneal astigmatism showed a significant decrease in both WTR and ATR groups in all measured points (all p < 0.05). Posterior corneal astigmatism showed no statistical difference in the WTR group and ATR subgroup 2 ( p > 0.05) and significant decrease in the ATR subgroup 1 ( p < 0.05) at 2 months postoperatively. Total corneal astigmatism showed significant decrease 2 months after surgery in the WTR group and ATR subgroup 1 (all p < 0.05), but not in the ATR subgroup 2 ( p > 0.05). According to correlation analysis based on trend line equations, 1.7 diopters of anterior astigmatism could expect 0.3 diopters of posterior astigmatism and 0.5 diopters of total astigmatism for the WTR group and 0.4 diopters of anterior astigmatism could expect 0.2 diopters of posterior astigmatism and 0.4 diopters of total astigmatism for the ATR group.

Considering the majority of cataract patients have vertically steep posterior corneal astigmatism, temporal incision for ATR patients is generally effective. Moreover, for patients with WTR astigmatism of more than 1.7 diopters or ATR astigmatism greater than 0.8 diopters, additional preoperative correction based on posterior astigmatism is needed for more precise prediction of postoperative total corneal astigmatism.