Handheld Tonometry Device Underestimates Intraocular Pressure

Handheld rebound tonometry devices tend to underestimate intraocular pressure (IOP) compared with applanation tonometry, according to research published in the Canadian Journal of Ophthalmology. However, 2 different handheld devices demonstrated good agreement with each other and an applanation tonometer, according to the report. 

Researchers enrolled 101 participants (mean age, 68.4±10.4 years; 61 women) who had glaucoma or were glaucoma suspects in the prospective, observational cross-sectional analysis. Participants underwent IOP measurement with 2 separate portable tonometry devices and an applanation tonometer and reported their comfort level for each device by rating it on a scale of 0 to 10 (0 least comfortable, 10 most comfortable). 

Overall, the investigators observed mean IOP measurements of 18.1±5.5, 18.2±5.9, and 20.4±6.1 mm Hg between handheld devices 1 and 2 and the applanation tonometer, respectively. The team noted good agreement between the 2 portable devices with an intraclass correlation coefficient (ICC) of 0.95 (P <.001) and good agreement between the 2 handheld devices and the applanation tonometer (ICC>0.80 for both, P <.001). Despite the good agreement, both handheld devices underestimated IOP by approximately 2 mmHg. Patients reported that the portable devices were more comfortable than the applanation tonometer (median comfort scores 9 for both portable devices, 7 for the applanation tonometer).   

“As new tonometers are introduced to the market, their IOP measurements compared with the [Goldmann applanation tonometer] IOP measurements are of considerable importance,” according to the researchers. “Underestimating IOP compared with the GAT can contribute to underdiagnosis and undertreatment of glaucoma, leading to irreversible vision loss from glaucoma. Overestimation of IOP compared with the GAT can contribute to overdiagnosis and overtreatment of glaucoma in patients without glaucoma.”

Study limitations include an overrepresentation of individuals reporting White ethnicity, the exclusion of individuals who do not have glaucoma or are not glaucoma suspects, and failure to repeat applanation tonometry measurements or check for agreement with a second examiner. 

Reference

Sachdeva R, Iordanous Y, Lin T. Comparison of intraocular pressure measured by iCare tonometers and Goldmann applanation tonometer. Can J Ophthalmol. Published online July 6, 2022. doi:10.1016/j.jcjo.2022.06.002