Background: To determine predictors of postoperative refractive astigmatism in cataract surgery for astigmatism correction by toric intraocular lens (IOL) implantation.
Methods: Prospective, observational case series. The right eyes of forty consecutive patients with preoperative corneal astigmatism of the total cornea of 1.5 diopters (D) or more in magnitude and scheduled for implantation of a non-toric IOL during cataract surgery with a 2.4-mm temporal clear corneal incision were examined prospectively. The vertical/horizontal astigmatism component (J0) and oblique astigmatism component (J45) of refractive and corneal astigmatism were converted using power vector analysis. Multivariate regression analysis was performed with refractive astigmatism at three months postoperatively as the dependent variable, and preoperative parameters including age, sex, refractive astigmatism, corneal astigmatism, sphere, spherical equivalent, intraocular pressure, corneal thickness, anterior chamber depth, lens thickness, axial length, and corneal higher order aberrations as independent variables. The root mean square (RMS) errors were calculated to express the regression model fit.
Results: The regression model for the J0 component was Postoperative refractive J0 = 1.05 × Coneal J0 - 0.14 (R2 = 0.96, P < 0.001). The model for the J45 component was Postoperative refractive J45 = 0.68 × Coneal J45 + 0.19 × Postoperative refractive J45 - 0.06 (R2 = 0.72, P < 0.001). The mean RMS errors for preoperative corneal astigmatism alone and the multivariate model were 0.58 D and 0.46 D, respectively. There was a statistically significant difference between them (P = 0.02).
Conclusions: Refractive astigmatism after implantation of a toric IOL can be predicted by the regression model using preoperative corneal and refractive astigmatism more accurately than by corneal astigmatism alone. However, the prediction of oblique astigmatism remains a challenge.