Comparison of corneal refractive power and astigmatism measured by CASIA2, IOLMaster 700 and Pentacam in cataract patients

To compare the difference and consistency of anterior corneal surface and total corneal refractive power and astigmatism measured by CASIA2, IOLMaster 700 and Pentacam in patients with age-related cataract.

A diagnostic test was conducted.Two-hundred patients (200 eyes) with age-related cataract were enrolled in Tianjin Medical University Eye Hospital from March to April 2021.The steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), degree and axis of astigmatism of the anterior and the total corneal surface of patients were measured by CASIA2, IOLMaster 700 and Pentacam, respectively.The astigmatism was transformed into J0 and J45 by Fourier transform formula.The differences and correlation of the measurements obtained with the three instruments were analyzed by one-way repeated measures analysis of variance and Pearson correlation analysis.The consistency was evaluated by Bland-Altman test.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Tianjin Medical University Eye Hospital (No.2021KY-07).

There were statistically significant differences in anterior corneal surface Kf and J0 measured by the three instruments (F=18.563, 16.172; both at P=0.001). The Kf measured by CASIA2 was significantly higher than that measured by IOLMaster 700, and the J0 measured by IOLMaster 700 was significantly higher than that measured by Pentacam (both at P<0.05). There were statistically significant differences in total corneal Ks, Kf, Km and J0 measured by the three instruments, which from IOLMaster 700 were the largest, followed by CASIA2, then Pentacam (F=1 300.447, 1 274.117, 1 609.713, 10.372; all at P=0.001). Pearson correlation analysis showed that the corneal refractive power measured by the three instruments was highly correlated (all at r>0.935, P<0.01), and the correlation of astigmatism values was weaker than the corneal refractive power (r=0.623-0.908, all at P<0.01). Bland-Altman analysis showed that the three instruments had good consistency in measuring the anterior corneal surface refractive power, anterior corneal surface astigmatism and total corneal astigmatism, which were clinically acceptable, while the consistency of total corneal refractive power measurement was poor.The difference in measuring total corneal refractive power was large between IOLMaster 700 and Pentacam, and relatively small between CASIA2 and Pentacam.

The consistency of CASIA2, IOLMaster 700 and Pentacam is good in measuring the anterior corneal surface refractive power of patients with age-related cataract, which can be substitutable, but poor in measuring the total corneal refractive power.The total corneal refractive power measurement from IOLMaster700 is the largest, the smallest from Pentacam, which is not recommended to be clinically exchangeable.