Comparative study of recording intraocular pressure in adults by three different tonometers Goldmann applanation tonometer, noncontact tonometer, and tonopen

Abstract

To compare and correlate the intraocular pressure (IOP) measurement obtained by Goldmann applanation tonometer (GAT), noncontact tonometer (NCT), and tonopen in normal and glaucomatous patients. A cross-sectional, observational, and comparative study was carried out. Two hundred eyes of 100 patients were screened, detailed history was taken, and thorough ocular examination was done. IOP was recorded using NCT (Keeler Pulsair), Tonopen (Tonopen XL), and GAT. Gonioscopy, optic disc examination, central corneal thickness, and visual field testing were done. The mean age of the study group was 53.25 years. Mean IOP by NCT was 19.20 mmHg, by GAT was 22.44 mmHg, and by tonopen was 19.33 mmHg. There was statistically significant difference between mean IOP with respect to method used (P<0.001). Forty-eight percent of eyes, 40% eyes, and 49% eyes had IOP less than 18 mmHg by NCT, GAT, and tonopen, respectively. In total, 35.5% eyes, 19.5% eyes, and 35.5% eyes had IOP ranging between 18 and 25 mmHg by NCT, GAT, and tonopen, respectively. In total, 16.5% eyes, 40.5% eyes, and 15.5% eyes had IOP more than 25 mmHg by NCT, GAT, and tonopen, respectively. NCT and tonopen readings correlate well with GAT readings in physiologic IOP range up to 20 mmHg, but at higher IOP range they tend to underestimate IOP readings as compared with GAT. However, NCT and tonopen can be used for screening purpose as they are portable and easy to use.