Intraocular pressure difference in Goldmann applanation tonometry versus Perkins hand-held applanation tonometry in overweight patients

Abstract

Objective: To analyze the increase in intraocular pressure (IOP) caused by anatomic and physiologic factors in overweight patients when using Goldmann applanation tonometry.

Design: A prospective cohort study.

Participants: Seventy average-weight individuals who had no difficulties with IOP measurements at the slit lamp and 12 obese patients with suspected glaucoma who could position the head at the slit lamp only with great effort participated.

Intervention: The authors compared IOP values between slit-lamp-mounted Goldmann applanation tonometry and Perkins hand-held tonometry.

Main outcome measure: The difference in Goldmann and Perkins IOP measurements was examined.

Results: In the group of obese patients, the mean IOP was 20.9+/-2.28 mmHg (mean +/- standard deviation; range, 18-26 mmHg) for the right eye and 21.4+/-3.16 mmHg (range, 16-28 mmHg) for the left eye when determined by Goldmann tonometry and 16.3+/-2.39 mmHg (range, 13-20 mmHg) for the right eye and 16.3+/-2.42 (range, 11-19 mmHg) for the left eye when determined by Perkins tonometry. The mean decrease was 4.5+/-1.3 mmHg (range, 3-7 mmHg) for the right eye and 4.9+/-1.9 mmHg (range, 2-9 mmHg) for the left eye. In the control group, the mean difference between the two types of tonometers for the right eye was 0.34+/-0.69 mmHg and for the left eye was 0.33+/-0.82 mmHg. Patients who had a falsely elevated IOP on Goldmann tonometry had an average body mass index of 34+/-3.82 (range, 28.5-41.9); most were female (5:1 ratio).

Conclusion: The authors believe simultaneous breath-holding and thorax compression, with subsequent increase in venous pressure, may be a causative factor for transitory elevations of IOP. Perkins tonometry in obese patients may help avoid a false diagnosis of glaucoma caused by transitory elevations in IOP.