Comparison of the Accuracy of Intraocular Pressure Measurement by Goldmann Applanation Tonometer and Keeler Noncontact Tonometer

Glaucoma is one of the leading causes of blindness, and its major risk factor is elevated intraocular pressure. Intraocular pressure measurement is a major examination in patients with glaucoma for diagnosis and treatment follow-up. This study was carried out with the purpose of comparing the accuracy of two types of conventional tonometers for measuring intraocular pressure. In this descriptive cross-sectional study, after complete ophthalmologic examinations, intraocular pressure was measured in 142 patients (284 eyes), two times at 5-minute intervals using both Goldmann and Keeler tonometers. The obtained results were analyzed with paired t-test and Pearson’s correlation test. Mean intraocular pressure in subjects that were in normal pressure range (<21mmHg) was obtained 14.03±2.35mmHg with Goldmann tonometer, and 14.28±3.05mmHg with Keeler tonometer. The mean difference of the two methods was 0.25±0.70 (p=0.015) and the correlation coefficient between two methods was calculated 0.83 (p<0.0001). Mean intraocular pressure in high intraocular pressure range (³21mmHg) was obtained 26.16±5.1mmHg with Goldmann tonometer, and 26.92±5.58mmHg with Keeler tonometer. The mean difference of the two methods was 0.76±0.44 (p=0.003), and correlation coefficient between two methods was calculated 0.97 (p<0.0001). Based on the results of this study, both used tonometry methods had acceptable accuracy in normal intraocular pressure range, but in high-risk cases such as glaucoma, Goldmann applanation tonometer is preferred as the gold standard.