To evaluate changes in intraocular pressure (IOP) according to position using a portable rebound tonometer.

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.

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.

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.