Effect of repeated applanation tonometry on the accuracy of intraocular pressure measurements

Purpose: To evaluate the stability of successive applanation tonometry measurements in glaucomatous eyes. Methods: A prospective, comparative, randomized, and evaluator-masked study was conducted in a tertiary medical center. Sixty-seven patients with glaucoma attending our glaucoma clinic underwent four successive intraocular pressure (IOP) measurements with Goldmann-type applanation tonometry. Findings were compared with 70 patients scheduled for cataract surgery, similar in age and sex. The results were statistically analyzed with repeated measures analysis. Results: In the glaucoma group, the difference between the first and second IOP measurements was statistically significant (15.94 mmHg vs 14.9 mmHg, p<0.0001), as was the decrease in IOP from the first measurement to each of the other successive measurements. No significant change in IOP was noted in the control group (mean, 13.7 mmHg). Conclusions: Patients with glaucoma show a decrease in IOP on repeated applanation tonometry measurements. By contrast, in individuals without glaucoma, no significant decrease in IOP on repeated applanation tonometry measurements was found.