[The effect of body position on the results of central and paracentral rebound tonometry]

This study analyzes the fluctuations of intraocular pressure (IOP) and clarifies the error of paracentral rebound tonometry associated with change in body position.

The study included 45 healthy volunteers aged 25.4±2.1 years. First we performed rebound tonometry in the sitting position in the center of the cornea and 3-4 mm from the temporal and nasal sides (Icare-c, Icare-n, Icare-t, respectively) and bidirectional applanation tonometry (IOPcc - corneal compensated, IOPg - Goldmann tonometry). Then we measured Icare-c, Icare-n, Icare-t in the supine position, and after 5 minutes repeated Icare-c in the supine position. After this, we measured Icare-c, IOPcc and IOPg in the sitting position.

Initial IOPcc and IOPg were 4.6±2.8 and 14.8±2.8 mm Hg. Initial Icare-c, Icare-t, and Icare-n measurements amounted to 15.0±1.9, 15.7±1.5 and 16.3±1.3 mm Hg; in the supine position the measurements were 16.4±2.1, 17.2±1.7 and 17.1±1.9 mm Hg. Paracentral measurements differed from Icare-c in both sitting and supine positions; only between Icare-t and Icare-n measured in the supine position there were no significant differences. The results of Icare-c, Icare-t, and Icare-n in body position change were comparable. Icare-c measured after 5 minutes in the supine position increased up to 16.6±2.4 mm Hg. Final IOPcc and IOPg did not differ from the initial measurements. Final Icare-c was lower than the initial result by 0.8±0.2 mm Hg, and lower than both supine Icare-c measurements by 2.1±0.2 and 2.6±0.2 mm Hg.

Paracentral rebound tonometry findings exceed those of rebound tonometry in central cornea, but in body position change the alteration of measurements in the same points on the cornea are comparable. In the supine position IOP increases on average by 1.0-1.5 mm Hg compared to the sitting position.