Agreement between refractive and corneal astigmatism in pseudophakic eyes

To examine the agreement and relationship between refractive and corneal astigmatism in a population of pseudophakic eyes.

Patients of age at least 40 years, visual acuity 20/40 or better, and no ocular disease were included (n = 111). Refractive astigmatism was obtained by subjective refraction. Corneal astigmatism was measured by automated keratometry and Scheimpflug scanning analysis. All refractive values were converted to power vector components J0 and J45 for comparison and regression analysis of refractive versus corneal astigmatism. Main outcome measures were refractive and corneal astigmatism components.

Median single Jackson cylinder (J) was similar in refractive [0.37 diopter (D)], keratometric (0.46 D), and Pentacam astigmatism (0.49 D) (P = 0.157). Median J0 astigmatic component was slightly negative, indicating against-the-rule (ATR) astigmatism, in refractive and Scheimpflug, but not in keratometric astigmatism (refractive J0: -0.10 D; keratometric J0: 0.05 D; Pentacam J0: -0.08 D) (P = 0.049). J45 astigmatic component was nearly zero and similar with the 3 methods (P = 0.416). Refractive and keratometric J0 were significantly correlated (r = 0.7, P < 0.01), as well as the corresponding J45 values (r = 0.65, P < 0.01). Refractive and Pentacam astigmatic components were worse correlated (J0: r = 0.36, P = 0.01; J45: r = 0.45, P < 0.01). Keratometric and Pentacam astigmatic components were also significantly correlated (J0: r = 0.58, P < 0.01; J45: r = 0.51, P < 0.01).

Mean internal ATR astigmatism, which comes mainly from the posterior corneal surface, adds to anterior corneal astigmatism, resulting in ATR refractive astigmatism. Correlation between refractive and corneal astigmatism components is better when keratometric data are used.