Comparison of Goldmann applanation tonometer, noncontact tonometer, and TonoPen XL for intraocular pressure measurement in different types of glaucomatous, ocular hypertensive, and normal eyes

Purpose: To compare intraocular pressure (IOP) measurements by Goldmann applanation tonometer (GAT), noncontact tonometer (NCT), and TonoPen XL in glaucomatous, ocular hypertensive (OHT), and normal eyes, all with various central corneal thickness (CCT). Methods: In 508 subjects, IOP was measured by three different tonometers: GAT, NCT, and TonoPen. CCT was also measured. Results: There was a statistically significant difference between IOP measurements made using the three different tonometers (RMANOVA, P<0.0001). Both NCT/GAT and TonoPen/GAT differences were significantly associated with age, CCT, IOP, and glaucoma diagnosis (multiple regression analysis, all P≤0.05). CCT and IOP had the greatest effect on IOP measurement variance by different tonometers. IOP measurements made by NCT were consistently higher than those made by GAT; this difference increased both with IOP and CCT levels, but decreased with age and OHT. In addition, TonoPen overestimated the GAT in the eyes of subjects with OHT. Conclusion: IOP measurement differences between the three tonometers are affected by age, type of glaucoma, and especially CCT and IOP levels.