Correlations of anterior and posterior corneal parameters in Chinese myopic patients: a retrospective multicenter study.

Background: Whether the correlations between anterior and posterior corneal parameters vary according to different conditions is unknown. We aimed to investigate the anterior-to-posterior correlations of corneal parameters according to different refractive status and anterior segment dimension.

Methods: A total of 8,365 myopic eyes undergoing refractive surgery between 2017 and 2019 from multiple ophthalmic centers were consecutively included in the study. All the eyes underwent routine ocular examinations including corneal Scheimpflug imaging. Pentacam data of the eyes were retrieved from the machine and only results with image quality labelled as 'OK' were included. The anterior-posterior correlations of corneal curvature, astigmatism, eccentricity, and asphericity were assessed using Spearman's correlation test by grouping the eyes via different myopic groups and different quartile levels of six corneal and anterior chamber parameters [mean simulated corneal curvature (SimKm), pachy apex (PA), corneal volume (CV) and diameter, anterior chamber depth (ACD) and volume (ACV), respectively].

Results: The mean age of the patients was 25.1±5.4 years and mean manifest spherical equivalent (SE) of the eyes was -5.13±2.05 diopter (D). Strongly negative anterior-posterior correlations of the mean corneal curvature were observed, with similar correlation coefficients in all the myopic groups (R: -0.85 to -0.88, all P<0.001). The anterior-posterior correlations of corneal astigmatism (R: 0.65 to 0.75, all P<0.001), eccentricity (R: 0.27 to 0.38, all P<0.001), and asphericity (R: 0.29 to 0.41, all P<0.001) were all positive, with the correlation coefficients slightly different between the myopic groups. The anterior-posterior correlations of mean corneal curvature were strongly negative with similar correlation coefficients in all the quartile groups of six corneal and anterior chamber parameters (R: -0.84 to -0.91, all P<0.001), except Sim Km (R: -0.36 to -0.64, all P<0.001). The anterior-posterior correlations of corneal astigmatism were all positive with the correlation coefficients slightly different between the quartile groups of SimKm (R: 0.66 to 0.74, all P<0.001). The anterior-posterior correlations of corneal eccentricity (R: 0.30 to 0.44, all P<0.001) and asphericity (R: 0.33 to 0.45, all P<0.001) were positive and slightly different between the quartile groups of SimKm, PA, and CV. Factors influencing anterior-posterior correlations of corneal curvature, astigmatism, eccentricity, and asphericity were also identified (β varied from -4.50 to 0.38, all P<0.05).

Conclusions: The anterior-posterior correlations of corneal curvature, astigmatism, eccentricity, and asphericity are affected by the severity of myopia and some other corneal parameters.