Relationship between corneal astigmatism and the distribution of corneal thickness along different principal meridians

Abstract

Abstract Aim: To analyze the relationship between corneal astigmatism (CA) and the distribution of corneal thickness along different principal meridians. Methods: A total of 362 patients with 684 eyes who underwent preoperative examination for refractive surgery at Ineye Hospital of Chengdu University of TCM from April 2021 to August 2022 were included in the study. The automatic refractor was used to measure the degree and axis of CA. The Sim-K values and the mean corneal thickness of the principal meridian of maximum refractive power and the mean corneal thickness of the principal meridian of minimum refractive power were obtained using Sirius for the 3mm, 4.5mm, and 6mm range. The correlation between the difference in mean corneal thickness (dct) of the two principal meridians and CA measured by a computer refractometer was analyzed. Then, the participants were divided into three groups based on the degree of CA: low CA group: -1.00D~0.00D (210 eyes), moderate CA group: -2.00D~-1.25D (229 eyes), high CA group: ≤-2.25D (245 eyes). The range of dct values was analyzed for different degrees of CA. Results: There was a negative correlation between dct and CA in the 3mm, 4.5mm, and 6mm ranges (r=-0.220, P<0.001; r=-0.214, P<0.001; r=-0.199, P<0.001). There was no difference in dct between the low and moderate astigmatism groups within a 3mm range (P>0.05). However, there were significant differences in dct between the low and high, moderate and high astigmatism groups within a 3mm range, as well as among the low, moderate, and high astigmatism groups within a 4.5mm and 6mm range (P<0.05). Conclusion: The average corneal thickness of the principal meridian with maximum refractive power is thicker than that of the principal meridian with minimum refractive power. Additionally, as the degree of CA increases, the dct also increases. Corneal astigmatism is closely related to the distribution of corneal thickness in different principal meridians. In order to improve the accuracy of corneal astigmatism measurement, the factors of corneal thickness distribution in different principal meridians should be considered.