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Comparison of IOP measurements between ORA and GAT in normal Chinese
Andrew Lam1, Davie Chen, Roger Chiu
1School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China. andrew.kc.lam@polyu.edu.hk
Purpose:
To compare intraocular pressure (IOP) obtained from the ocular response analyzer (ORA) and Goldmann applanation tonometer (GAT) on a group of normal Chinese.
Methods:
One hundred twenty-five normal subjects were recruited, with one eye randomly selected for this study. Each eye was measured first with the noncontact tonometer ORA, followed by the GAT and ultrasound pachometry, in a randomized order. Four readings were obtained from the ORA, and three measurements were taken with the GAT. The mean was used for analysis. The ORA provided a Goldmann-correlated IOP (IOPg) and a corneal-compensated IOP (IOPcc). Three central corneal thickness (CCT) values were measured using an ultrasound pachometer, and the mean was used for analysis.
Results:
IOP obtained from the ORA was similar to that from the GAT (IOPg minus GAT: mean difference = 0.33 mm Hg, 95% limits of agreement = 4.55 to -4.44 mm Hg; IOPcc minus GAT: mean difference = 0.24 mm Hg, 95% limits of agreement = 4.83 to -5.07 mm Hg). CCT was positively associated with corneal hysteresis (CH) (r2 = 0.30, p < 0.01), corneal resistance factor (r2 = 0.38, p < 0.01), GAT (r2 = 0.09, p < 0.01) and IOPg (r2 = 0.16, p < 0.01). IOPcc was not associated with CCT (r2 = 0.01, p = 0.33).
Conclusions:
Both IOPg and IOPcc have good agreement with GAT on normal subjects. The influence of CCT on IOPcc was insignificant.
