Objective  To explore the variation in different corneal morphologies in Pentacam Scheimpflug tomography and the feasibility of assisting diagnosis of abnormal corneal posterior surface height. Methods  In this retrospective study 120 myopia patients (240 eyes) who underwent preoperative examination of corneal refractive surgery in Jiangsu province hospital from April 2020 to September 2020 were selected. All patients had a comprehensive eye refractive power examination, and were examined by Pentacam three-dimensional anterior segment analysis system. The anterior surface curvature (ASK), posterior surface curvature (PSK), anterior surface astigmatism (AAstig), posterior surface astigmatism (PAstig), central corneal thickness (CCT), corneal diameter (W-W), deviation (Df) of corneal anterior surface difference map, deviation (Db) of corneal posterior surface difference map and progress of corneal average thickness were selected from Pentacam anterior segment analysis system. They were divided into four groups according to corneal diameter, and the differences between groups and within groups were compared. Spearman rank correlation analysis was used to explore the related influencing factors of BAD-Do (belin/ambrosio enhenced ectasia display-overall deviation of normality), and a multiple linear regression model was established to find the main influencing factors of BAD-Do. Results  All patients included in the study were divided into four groups according to corneal diameter, including group A, B, C and D. There are 36 eyes in group A, 76 eyes in group B, 82 eyes in group C and 46 eyes in group D. There was no significant difference in refractive power between groups, that is, spherical power, cylindrical power and corneal thickness. Pentacam measurement showed that there were significant differences between PSK groups in patients with different corneal diameters. In the aspect of overall normal deviation BAD-Do, there were significant differences between group A, group C and D. There were also significant differences between group B, group C and D, but there is no significant difference between group A and group B. By analyzing the correlation between BAD-Do and Pentacam parameters in each group, it was found that BAD-Do had no statistical correlation with refractive power and corneal thickness (P> 0.05), but it had a low correlation with PSK (r=-0.27, P=0.001). In addition, there was a weak correlation between BAD-Do value and corneal diameter (r=-0.39, P=0.001). Conclusion Corneal diameter and posterior surface curvature are the main factors affecting BAD-Do. The smaller the corneal diameter, the more likely the patients will have BAD-Do abnormality. In the interpretation of Pentacam results, the influence of corneal diameter and corneal posterior surface curvature on the results should be considered.

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