Factors Influencing Discrepancies in Intraocular Pressure Measurements Between iCare IC200 and Goldmann Tonometer

Intraocular pressure measured by Goldmann applanation tonometry, central corneal thickness, and history of cataract surgery are factors in the discrepancies in intraocular pressure measurements between the iCare IC200 rebound tonometer and the Goldmann applanation tonometer.

To investigate the factors affecting the discrepancies in intraocular pressure (IOP) measurements between the iCare IC200 rebound tonometer (RBT) and the Goldmann applanation tonometer (GAT).

The IOP was measured sequentially using RBT followed by GAT. Bland-Altman analysis was used to determine the agreement between the RBT and GAT. Eyes were classified into 3 groups based on the difference calculated as RBT minus GAT: group A (-1 to 1 mm Hg), group B (≥3 mm Hg), and group C (≤-3 mm Hg). Logistic regression analysis was performed to identify the factors associated with the measurement discrepancies.

A total of 402 right eyes were included in the study. The RBT and GAT measurements were significantly correlated (Spearman r =0.885, P <0.001). The mean IOP differences between the RBT and GAT were 0.114±2.13 mm Hg (range: -7 to 8, 95% limit of agreement: -4.06 to 4.29 mm Hg). Multivariate logistic analyses revealed that greater central corneal thickness (CCT) ( P =0.002) was significantly associated with overestimation of IOP by RBT relative to GAT. We found that underestimated IOP by RBT relative to GAT in patients with higher GAT-measured IOP ( P =0.002) and those with a history of cataract surgery ( P =0.006).

RBT tends to overestimate IOP relative to GAT in patients with thicker CCTs, while it underestimates IOP in those with higher GAT-measured IOP or a history of cataract surgery.