Analysing the correlation between differential corneal thickness along principal meridians and corneal astigmatism: implications for whole-eye astigmatism.

Abstract

Objective: This study aimed to analyse the correlation between corneal astigmatism and disparity in corneal thickness.

Methods: In this retrospective analysis, data from 342 patients (684 eyes) were collected. The Sirius three-dimensional corneal topography system was utilised to ascertain the mean corneal thickness of the meridians. Correlation analyses were conducted between the mean difference in corneal thickness along the two principal meridians and the astigmatic values computed by simulated keratometry values (Sim-K) for total corneal astigmatism (TCA) and posterior corneal astigmatism (PCA), respectively. Variability in differential corneal thickness (DCT) values at different TCA levels was analysed. The variability of DCT within the 3-mm corneal range at different differences between whole-eye astigmatism and TCA (Difference between corneal astigmatism and computer optometry, DWT) levels was analysed.

Results: Within the ranges of 3, 4.5, and 6 mm, the mean corneal thickness of the meridian with the maximum refractive power (Sim-K₂) was greater than that of the meridian with the minimum refractive power (Sim-K₁) (P < 0.05). The TCA showed a negative correlation with DCT across all three ranges (P < 0.001), whereas PCA exhibited a positive correlation with DCT (P < 0.001). A difference was observed among the TCA groups within each range, with DCT increasing alongside the dioptre of astigmatism (P < 0.05). In the 3 mm corneal range, an increase in the difference in corneal thickness was associated with an increase in the difference between whole-eye astigmatism and TCA (P < 0.05).

Conclusion: The meridian with the maximum refractive power had a thicker mean corneal thickness than the meridian with the minimum refractive power. The difference in corneal thickness is closely related to the severity of corneal astigmatism. The extent of residual astigmatism is influenced by this thickness difference.