Pentacam and Corvis ST findings in myopic Chinese patients with different corneal diameters in Singapore

Purpose: To study the effect of corneal white-to-white diameter on Pentacam Scheimpflug cornea tomography and Corvis ST corneal visualization Scheimpflug technology parameters in myopic eyes.

Methods: In this retrospective cross-sectional study, 190 eyes of 190 Chinese myopic patients (spherical equivalent range: -1.25 D to -11.00 D) assessed for refractive surgery using Pentacam and Corvis ST devices were included. Patients were divided into groups based on corneal diameter: group A <12 mm, and group B ≥12 mm. Age, gender, spherical equivalent, Pentacam variables, and Corvis ST variables were collected. Statistical analysis was performed using IBM SPSS Statistics (Version 28.0).

Results: There were 110 patients in group A and 80 patients in group B, with no statistically significant difference in age, gender, or spherical equivalence. For Pentacam data, group A had significantly higher Belin/Ambrosio Enhanced Ectasia Display (BAD-D) scores than group B (0.88 vs. 0.44) and pachymetric progression index (minimum, average, and maximum), and steeper front keratometric values, whereas group B had larger anterior chamber depth and maximum Ambrosio-relational thickness (ARTmax) (462.54 vs. 503.93). BAD-D indices, pachymetric progression indices, and front keratometric values had negative correlations with corneal diameter, whereas ARTmax and back keratometric values had positive correlations. For Corvis ST data, group A had a significantly higher corneal biomechanical index (CBI) (negatively correlated) while group B had a higher Ambrosio relational thickness to the horizontal profile (ARTh) (473.60 vs. 570.78) (positively correlated).

Conclusion: Corneal diameter influences both Pentacam and Corvis ST parameters, with smaller corneal diameters having a higher BAD-D and a lower ARTmax and ARTh. In addition, this is the first study to report a correlation between posterior surface corneal power and corneal diameter. As refractive surgery evaluation relies on these parameters, taking corneal diameter into account would improve both sensitivity and specificity in pre-refractive surgery screening for ectasia/keratoconus.