Effects of repetitive IOP measurements

Purpose The purpose of this study was to evaluate the effect of repetitive applanation tonometry measurements on IOP and aqueous humor volume in the anterior chamber. Methods This is an ongoing study where four healthy volunteers have participated so far. Consecutive repeated series of six measurements with Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) were made alternately on both eyes for one hour. Using an Oculus Pentacam, the anterior chamber of the left eye was photographed before the measurements and then consecutively for 20 min. Finally, one additional measurement was performed with both GAT and ART. Results In this abstract we present the results from the first four subjects. The results show that there was a significant reduction in IOP on the right eye both with GAT and ART. After one hour of measurements, IOP was reduced by 5.5 mmHg (range 4.3-7.2 mmHg) for GAT and 3.1 mmHg (range 1.0-4.1 mmHg) for ART. The decrease in aqueous humour volume after IOP measurements was less than 10 % for all subjects. Conclusion Although Bechrakis showed as early as 1966 that repetitive measurements result in significant IOP reduction, the mechanism behind this is still matter of debate. Our preliminary results confirm the occurrence of IOP reduction after repetitive measurements, but indicate that it could not be explained by the decrease in volume of the anterior chamber.