Axis difference between corneal and internal astigmatism to consider for toric intraocular lenses

Abstract

Purpose: To evaluate the axis difference between corneal and internal astigmatism in patients with cataract, because if the axis of corneal astigmatism is opposite to the axis of internal astigmatism, the amount of refractive astigmatism will increase after cataract surgery owing to disappearance of the neutralizing effect of the crystalline lens on corneal astigmatism.

Design: Retrospective cross-sectional study.

Methods: One hundred eighty patients (180 eyes) who underwent cataract surgery were enrolled. Preoperative refractive, corneal, and internal astigmatism were measured using a wavefront analyzer and retrospectively analyzed. On-axis was defined as an axis difference between corneal and internal astigmatism of 180 ± 10 degrees. Opposite-axis was defined as an axis difference between corneal and internal astigmatism of 90 ± 10 degrees. The remaining cases were defined as oblique-axis.

Results: Corneal and internal astigmatic vectors showed a tendency to have the opposite direction. An on-axis difference was seen in 10.0% of patients (18 eyes), oblique-axis in 69.4% of patients (125 eyes), and opposite-axis in 20.6% of patients (37 eyes). Of all eyes, 10.0% had an opposite-axis difference with more than 1.00 diopter (D) of both corneal and internal astigmatism. The percentage of eyes with an opposite-axis difference between corneal and internal astigmatism had a tendency to increase as corneal and internal astigmatism increased (P = .030 and P = .003, respectively).

Conclusions: A total of 10.0% of all eyes with cataract had an opposite-axis difference with more than 1.00 D of both corneal and internal astigmatism. In these cases, surgical techniques to reduce corneal astigmatism, such as a toric intraocular lens, should be recommended to increase patient satisfaction.