A comparison of Icare PRO and Perkins tonometers in anesthetized children

Abstract

Aim: To compare intraocular pressure (IOP) measurements obtained with the Perkins applanation tonometer (PAT) and Icare PRO (ICP) rebound tonometer in anesthetized aphakic or strabismus children. Furthermore, intra-operator and inter-operator correlation have been evaluated, along with the effects of Central Corneal Thickness (CCT) on IOP measurements.Methods: Seventy children undergoing examination under anesthesia with sevofluorane for aphakic patients and for surgery for strabismus were included. IOP have been measured twice immediately after anesthesia induction with both PAT and ICP in one eye, and by two different operators with both devices in the fellow eye. Furthermore, CCT was measured with ultrasound pachymetry Pacline (Optikon). Agreement between the devices measuremente has been evaluated using Bland-Altman analyses. Repeatability and reproducibility of the device have been evaluated with Intraclass Correlation Coefficient (ICC) with a value >0.75 associated with excellent reliability.The relationship between IOP and CCT has been evaluated with Spearman's correlation coefficient r and determination coefficient r 2 .Results: Mean difference in IOP measurements between ICP and PAT was 1.97 mmHg ± 1.23 mmHg (p < 0.05). This difference appeared to be higher in aphakic patients (mean difference 2.15 ± 1.35) than in patients undergoing strabismus surgery (mean difference 1.83 mmHg ± 1.12).ICC Intraclass Correlation Coefficient is used to evaluate repeatability and reproducibility, that are both high for PAT (repeatability 0.96, reproducibility 0.76) compared with ICP (repeatability 0.81, reproducibility 0.70). Correlation coefficient between CCT and IOP is 0.66 for both ICP and PAT. Conclusion: ICP tends to overestimate IOP compared to PAT. Repeatability and reproducibility are both high for PAT as compared to ICP. A significant correlation between IOP and CCT for both instruments has been demonstrated.