IOPen underestimates IOP measurements

The IOPen rebound tonometer underestimates intraocular pressure (IOP) measurements compared to Goldmann applanation tonometer (GAT) and ocular response analyzer (ORA), reveals a study published in Eye.

Dr J. Moreno-Montañés et al., Department of Ophthalmology, Clínica Universidad de Navarra, Pamplona, Spain, conducted a cross-sectional, randomized study on 198 normal eyes. The Bland and Altman limits of agreement (LoA) were used to calculate agreement between all three tonometers.The median IOPen IOP was 3 mm Hg below the GAT and the ORA IOP. LoA width between the IOPs of the IOPen and the GAT ranged between 13.92 and 15.99 mm Hg. Central corneal thickness (CCT) was not linked to the IOPen measurements, but corneal hysteresis (CH) and corneal rigidity factor (CRF) were linked to measurements by IOPen and GAT.

IOPen underestimated the IOP compared with GAT and ORA. The effect of measurement quality or measurement order on IOPen was low. CCT did not affect the IOPen, but the CH and CRF did. The LoA width between the IOPen and GAT IOPs was higher than between the ORA IOPg or ORA IOPcc and GAT IOPs.