Accuracy and Reliability of the Icare PRO in Enucleated Porcine Eyes - Upright and Horizontal Positions

PURPOSE: To compare the accuracy and reliability of intraocular pressure (IOP) measurements in enucleated porcine eyes using the Icare PRO in the upright and horizontal positions. METHODS: We designed an enucleated porcine eye model whose anterior chamber was cannulated with a 30-gauge needle, connected in parallel to a pneumatic pressure device. The reference pressure was manipulated by changing the air pressure from 70 to 10 mm Hg at 10 mm Hg intervals, and the IOP of porcine eyes was measured with the Icare PRO at each pressure. Correlation analysis, comparison using the Bland-Altman plot and Wilcoxon signed rank test, was performed to assess the accuracy of IOP measurements. Intraclass correlation coefficients were calculated to assess the intra-observer variability in the upright and horizontal positions, respectively. RESULTS: The IOP value in both upright and horizontal positions was well correlated with the reference pressure (r = 0.992 and 0.985, respectively). The Bland-Altman plot showed good agreement between the two positions. However, all IOP values in both positions were lower than the reference pressures. The IOP values in the horizontal position were significantly lower than those in the upright position at the a reference pressure of 50 mm Hg or greater. Values of intraclass correlation coefficient ranged from 0.911 to 0.984 when measured in the upright position and from 0.707 to 0.914 in the horizontal position. CONCLUSIONS: IOP measurements of Icare PRO in porcine eyes were remarkably lower than reference pressures controlled by the pneumatic method even though they showed a good correlation with reference values. The higher was the reference pressure, the greater was the degree of underestimation of IOP measurement in both positions. This trend was more pronounced in the horizontal position, and the reliability of IOP measurements was also lower than that in the upright position.

Comparison of Intraocular Pressures According to Position Using Icare Rebound Tonometer

PURPOSE: To evaluate changes in intraocular pressure (IOP) according to position using a portable rebound tonometer. METHODS: We measured the IOP values of 20 healthy volunteers (40 eyes) in the sitting, supine, right lateral decubitus and left decubitus positions with a portable rebound tonometer, and then analyzed using the Wilcoxon signed rank test. IOP in sitting position was also measured with a non-contact tonometer and a Goldmann applanation tonometer, and analyzed with Kruskal-Wallis test and Spearman correlation analysis. Agreement among the 3 tonometers was calculated using the Bland-Altman method. RESULTS: The IOP measured with rebound tonometer in the supine position was significantly higher than in the sitting position (p = 0.002). However, there was no significant difference in IOP between the supine and decubitus positions. In the decubitus position, there was no significant difference in IOP between the dependent and non-dependent eyes. IOP measurement using the rebound tonometer showed positive correlation with that of the noncontact and Goldmann applanation tonometers. CONCLUSIONS: In normal subjects, IOP measurement obtained with a rebound tonometer in the supine position was significantly higher than in the sitting position, but there was no significant difference in IOP between the supine and decubitus positions. A rebound tonometer may be useful for patients whose intraocular pressure measurement with Goldmann applanation tonometer or non-contact tonometer is impossible. When using a portable rebound tonometer in bed-ridden or pediatric patients, we should pay attention to the interpretation of IOP in the supine position.