Agreement Between Icare Home and Goldmann Applanation Tonometry in Eyes With Keratoconus: Influence of Corneal...

Accurate intraocular pressure (IOP) measurement is essential for glaucoma management. However, corneal irregularities may affect the tonometer's accuracy. This study aims to assess the agreement between Icare Home (ICH) rebound tonometry and Goldmann Applanation Tonometry (GAT) in patients with keratoconus and to investigate the impact of corneal parameters and keratoconus severity on IOP measurements.

In this cross-sectional study, 48 eyes of 25 patients with keratoconus underwent same-day IOP measurements with GAT and ICH. Agreement between methods was analyzed using Bland-Altman plots. Spearman rank correlation was used to assess associations between IOP and corneal parameters.

The mean IOP was 11.98 ± 2.52 mm Hg for GAT and 10.45 ± 2.85 mm Hg for ICH. The mean absolute difference between devices was 2.65 ± 2.16 mm Hg ( P <0.001), and the mean arithmetic difference was 1.53 ± 3.06 mm Hg ( P = 0.0018), with 54.17% of cases falling within the ±2 mm Hg. Bland-Altman analysis showed 95% limits of agreement from -4.47 to 7.53 mm Hg. ICH IOP was positively correlated with MCT (ρ = 0.389, P = 0.0063) and negatively correlated with astigmatism (ρ = -0.512, P = 0.0002), Kmax (ρ = -0.411, P = 0.0037), K1 (ρ = -0.515, P = 0.0002), and K2 (ρ = -0.43, P = 0.0023). GAT IOP showed no significant correlation with these parameters.

ICH underestimated IOP compared with GAT, with substantial variability between the methods. Corneal parameters were significantly associated with ICH readings. These findings highlight the limited reliability of ICH in advanced keratoconus, where clinically significant measurement differences may affect patient management.