Abstract
Purpose :
To determine the variability in intraocular pressure (IOP) with postural change and evaluate the agreement between Goldmann Applanation, Tonopen, and Perkins Tonometry
Methods :
Participants aged ≥ 22 years were recruited from two tertiary glaucoma clinics. Eyes with central corneal thickness <500µm or >600µm, prior incisional glaucoma or any corneal surgery, or any corneal pathology were excluded. One eye (higher IOP or randomly selected if same IOP in both eyes) per participant was tested. IOP was measured in the sitting position with the Goldmann Applanation Tonometer (GAT; Haag Streit). Participants were then placed in the supine position, after which supine IOP was measured by the Tonopen Avia (TP; Reichert) followed by the Perkins MK2 (Clement Clarke) tonometers. Each measurement was repeated twice, and a third measurement was taken if readings were >2mmHg apart; the mean or median IOP was used for analysis, respectively. Paired t-tests were used to test for statistical differences in measurements between tonometers. Bland-Altman plots were used to depict mean differences (MD) and 95% limits of agreement (LOA)
Results :
Data from 118 eyes of 118 participants (56% female) were included in the analysis (we excluded one participant with three highly disparate measurements by TP). Mean ±SD GAT (sitting), Perkins (supine) and TP (supine) measurements were 17.0 ±5.2, 16.8 ±4.6 and 17.2 ±3.8 mmHg, respectively. The overall MD (LOA) between GAT (sitting) and Perkins (supine) [Fig.1], and Perkins and TP (both supine) [Fig.2] were 0.2 (-4.3 to 4.8), and -0.4 (-5.8 to 4.9), respectively. Bland-Altman plot showed higher IOP by Perkins (supine) when compared to GAT (sitting) at low IOP and lower by Perkins at high IOP [Fig.1]. There were no differences in overall IOP measurements in the sitting and supine positions (GAT vs. Perkins, p=0.25) as well as between tonometers in the supine position (Perkins vs. TP, p=0.08)
Conclusions :
IOP overall was similar comparing sitting to supine, but supine measures were higher at lower IOP and lower at higher IOP. In the supine position, overall IOP measurements were similar between Perkins and Tonopen
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.