Falsely high rebound tonometry.

BACKGROUND

Rebound tonometry (RBT) can be used to measure intraocular pressure (IOP) in children unable to tolerate measurement with applanation tonometry (AT) while awake. RBT readings are often 2-3 mm Hg higher than AT. We have experienced children with a repeatedly higher difference between RBT and AT measurements (≥6 mm Hg). The purpose of this study was to identify demographic and ocular characteristics that contribute to this artifactuous discrepancy.

METHODS

The medical records of pediatric patients with IOP measured by RBT followed by AT within 6 months without intervening surgery or change in medical management were retrospectively reviewed to identify potential predictors of greater difference between RBT and AT readings.

RESULTS

A total of 123 eyes of 65 patients were included. In patients with normal IOP (≤24 mm Hg), 18.5% had a ≥6 mm Hg difference between RBT and AT, with RBT being higher. Risk factors for this included presence of persistent fetal vasculature (PFV), increased corneal diameter, and higher initial RBT value (>20). In patients with elevated IOP (>24 mm Hg), 77% had ≥6 mm Hg difference, with larger corneal diameter being the sole predictor. Eyes were less likely to have significant RBT-AT difference if there was corneal opacity or iris abnormalities in eyes with elevated IOP (>24 mm Hg).

CONCLUSIONS

In some children, RBT readings are ≥ 6 mm Hg higher than AT readings. Caution should be taken when interpreting RBT values in patients with PFV, increased corneal diameter, and higher initial RBT values.