Influence of Biometric and Corneal Tomographic Parameters on Normative Corneal Aberrations Measured by Root Mean Square

Background/Objectives: To determine the impact of corneal and biometry parameters on the normative root mean square (RMS) values of corneal aberrations measured at a 6 mm diameter. Methods: The RMS values for corneal aberrations (anterior, posterior, and total) were measured along with corneal parameters using Scheimpflug tomography on 770 normal subjects. The biometric parameters were measured with an optical biometer. A multiple linear regression model was used to assess the effect of these parameters on the RMS values for corneal aberrations. Results: The mean RMS values for low-order (LOAs) and high-order 6 mm aberrations (HOAs) were 1.883 ± 0.797 µm and 0.484 ± 0.173 µm, respectively, and for the anterior and posterior cornea, the values were 0.775 ± 0.166 µm and 0.189 ± 0.036 µm, respectively. For the anterior cornea, the main predictors of the RMS LOAs (R² = 69.8%) were anterior corneal astigmatism (ACA) and anterior corneal elevation (Ele F) on the apex (both p < 0.0001) and for the RMS HOAs (R² = 33.3%) the main predictors were age, ACA, and Ele F on the thinnest point (all p < 0.0001). For the posterior cornea, considering only the posterior corneal variables, the main predictors of the RMS LOAs (R² = 63.4%) were posterior corneal astigmatism and posterior corneal elevation (Ele B) on the thinnest point and apex (all p < 0.0001) and for the RMS HOAs (R² = 46%) the main predictors were the mean posterior keratometry and Ele B on the thinnest point and apex (all p < 0.0001). Conclusions: Normative data of RMS values for corneal aberrations measured over 6 mm are influenced by age and several corneal parameters, which should be considered when evaluating the diagnostic ability of the RMS values.