Comparison of intraocular pressure measurements between Easyton transpalpebral tonometry and Perkins, iCare iC100 and Corvis ST, and the influence of corneal and anterior scleral thickness.

Purpose: To compare intraocular pressure (IOP) measurements between Easyton transpalpebral tonometry and Perkins, iCare iC100 and Corvis ST. Also, to assess the influence of corneal characteristics and anterior scleral thickness (AST) on the IOP measurements.

Methods: Sixty-nine eyes from 69 healthy subjects were included. IOP was measured by Easyton, Perkins, iC100 and Corvis ST (corrected IOP, bIOP; and non-corrected IOP, IOPnct). Other variables studied were AST, axial length (AL), and Corvis parameters: Length 1, velocity 1, length 2, velocity 2, peak distance, radius, deformation amplitude, and central corneal thickness (CCT). Pearson correlation, limits of agreement (LoA), and multiple regression analysis were calculated.

Results: No significant differences in IOP between Easyton and Perkins, iC100, and bIOP were observed (all p > 0.05), being significant only between Perkins and IOPnct ( - 1.49 mmHg, p < 0.001). Bland-Altman graphs showed that the mean difference between Perkins and Easyton was 0.07 mmHg (p < 0.001), and LoA  - 7.49 to + 7.39 mmHg. Significant correlations were found between the measurements of Perkins and iC100, IOPnct, bIOP (r = 0.710, 0.628, 0.539; p < 0.001 respectively), iC100 and IOPnct, bIOP (r = 0.627, 0.513; p < 0.001, respectively). The multivariate regression analysis revealed that differences between Perkins and Easyton (adjusted R = 0.25) were influenced by AL (B = 1.28, p < 0.008), length 1 (B = 3.13, p < 0.018), and the radius (B = 1.26, p < 0.010). Differences between Perkins and bIOP (adjusted R = 0.21) were affected by the CCT (B = 0.029, p < 0.003).

Conclusions: There are no significant differences in the IOP measurements between Perkins and Easyton, iC100 or bIOP. Length 1, radius, and CCT have limited influence on these differences, while AST did not show any effect.