Aim: The aim of this study is to compare intraocular pressure (IOP) in healthy eyes measured via dynamic bidirectional applanation and air-puff tonometry, and to evaluate the effect of age, gender, the spherical equivalent (SE), mean keratometry (Kmean), corneal hysteresis (CH), and the corneal resistance factor (CRF) on IOP measurements.
Materials and methods: IOP measured in 956 healthy eyes using the ocular response analyzer (ORA) and air-puff tonometer was compared in this cross-sectional retrospective study. Correlations between IOP, and age, gender, SE, Kmean, CH, and CRF were investigated using univariate and multivariate analyses. Bland–Altman plots were used to determine the level of agreement between the IOP values obtained with the two devices: IOP via air-puff tonometer (IOP-air-puff) and corneal-compensated IOP (IOPcc) using ORA (ORA-IOPcc). Linear mixed modeling was used to evaluate the effects of the study parameters on IOP. Intermethod reliability was established by calculating intraclass correlation coefficients (r).
Results: The mean age of the patients was 39.56 ± 14.44 years. The mean IOPair-puff and ORA-IOPcc were 16.72 ± 2.37 mm Hg and 13.75 ± 3.12 mm Hg, respectively (p < 0.001). The mean CH and CRF were 11.14 ± 1.61 mm Hg and 10.53 ± 1.65 mm Hg, respectively. Multivariate analysis showed that both CH and CRF were significantly correlated with IOP-air-puff and ORA-IOPcc (p < 0.001). The 95% limit of agreement for IOP-air-puff and IOPcc was −2.843 to 8.784. There was a significant correlation between IOP-air-puff and ORA-IOPcc (r = 0.443, p < 0.001); the R2 value was 0.196.
Conclusion: A low degree of agreement was noted between IOP-air-puff and ORA-IOPcc. The present findings show that air-puff tonometry overestimates IOP, as compared to ORA.
Clinical significance: IOP based on air-puff tonometry must be interpreted in conjunction with other ophthalmologic findings and the same IOP measuring device should be used for follow-up evaluations.
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