Influence of posterior corneal astigmatism on the outcomes of toric intraocular lens implantation in eyes with oblique astigmatism.

Abstract

To assess whether the outcomes of toric intraocular lens (IOL) implantation in eyes with oblique astigmatism can be improved by direct measurements of posterior corneal astigmatism using anterior segment optical coherence tomography (AS-OCT) instead of by using anterior corneal measurements alone. Retrospective case series. Two toric IOL power calculation methods were compared: anterior corneal astigmatism was used in the keratometry group, whilst total corneal astigmatism determined by ray tracing through the measured anterior and posterior corneal surfaces was used in the AS-OCT group. In a total of 279 eyes of 232 patients, subgroup analysis was conducted for with-the-rule (WTR) (85 eyes in the keratometry group and 34 eyes in the AS-OCT group), against-the-rule (ATR) (73/29 eyes), and oblique (26/32 eyes) astigmatism. In the WTR and ATR astigmatism groups, the uncorrected distance visual acuity (UDVA) was significantly better in the AS-OCT group than in the keratometry group (P = 0.012 and P < 0.001, Mann-Whitney test), and the residual astigmatism was significantly smaller in the AS-OCT group than in the keratometry group (P = 0.037 and P < 0.001). In eyes with oblique astigmatism, the UDVA (P = 0.299) and residual astigmatism (P = 0.373) of the keratometry and AS-OCT groups did not differ. Incorporation of posterior corneal astigmatism measured with AS-OCT can significantly improve the outcomes of toric IOL implantation in eyes with WTR and ATR astigmatism, but not in eyes with oblique astigmatism.