Agreement Between Icare Home And Goldmann Applanation Tonometry In Eyes With Keratoconus: Influence Of Corneal Parameters On Intraocular Pressure Measurements

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

This study was conducted at the cornea clinic of Shamir Medical Center, Be’er Ya’akov, Israel. Patients with keratoconus were recruited during routine follow-up visits. Data collection included demographic details, ophthalmic history, and corneal imaging with Pentacam topography. Intraocular pressure measurements were obtained using GAT and ICH in a standardized clinical setting.

This cross-sectional observational study included 48 eyes of 25 patients with keratoconus. IOP was measured using GAT and ICH during the same clinic visit, and the agreement between methods was analyzed using Bland-Altman plots. The correlation between IOP measurements and corneal parameters, including minimal corneal thickness, astigmatism, and keratometric values (Kmax, K1, K2), was assessed using Spearman’s rank correlation for both GAT and ICH.

The mean IOP was 11.98±2.52 mmHg for GAT and 10.45±2.85 mmHg for ICH. The mean IOP difference (GAT - ICH) was 1.53±3.06 mmHg (p = 0.0018, Mann-Whitney U test), with 54.17% of cases falling within the ±2 mmHg agreement limits. Bland-Altman analysis showed 95% limits of agreement ranging from -4.47 to 7.53 mmHg. ICH IOP was significantly correlated with minimal corneal thickness (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 = -0.430, p = 0.0023). No significant correlations were found between ICH IOP and time since CXL (p = 0.2853). GAT IOP showed no significant correlation with corneal parameters or visual acuity.

ICH underestimated IOP compared to GAT, with substantial variability between the methods. Corneal parameters, particularly keratometry and minimal corneal thickness, influenced ICH readings but not GAT. These findings suggest that ICH measurements in patients with corneal irregularities should be interpreted with caution.