Comparative study of measurement of intraocular pressure in eyes with corneal opacity and normal cornea by Tonopen Avia, rebound tonometer (I-care), and noncontact tonometer

Abstract

Purpose: The most common indications for keratoplasty are patients with corneal opacity. The presence of glaucoma prior to keratoplasty is an important risk factor, eventually may lead to failure of the corneal graft. Currently, we have insufficient evidence of comparison of intraocular pressure (IOP) measurement in patients with corneal opacity. The purpose of this study is to analyze the IOP measurements obtained with Tonopen (TP) Avia, I-Care rebound tonometer, and noncontact tonometer (NCT) in patients with corneal opacity and normal cornea. Materials and Methods: It is a prospective, comparative study using a convenience cohort of eyes with corneal opacity. Patients having corneal opacity and normal cornea had IOP measured using TP (Avia-Reichert, Depew, Newyork, USA), rebound tonometer (I-care), and NCT (Reichert AT 555). IOP measurements were compared and agreement assessed. Bland–Altman plots, box–whisker plot, and error–bar diagram were used for assessing agreement. Results: Thirty eyes with corneal opacity and thirty eyes with normal cornea of the same patients were included in the study. The mean IOP readings in eyes with normal cornea taken by NCT, rebound tonometer, and TP Avia were 13.71 mm Hg with standard deviation (SD) of 2.73, 14.85 mm Hg with SD of 2.13, and 14.73 mm Hg with SD of 2.27, respectively. The mean IOP readings in eyes with corneal opacity taken by NCT, rebound tonometer, and TP Avia were 17.35 mm Hg with SD of 5.82, 15.83 mm Hg with SD of 3.2, and 15.98 mm Hg with SD of 3.53, respectively. Bland–Altman analysis plots show good agreement between all three devices. Conclusion: IOP measurements in normal cornea showed underestimation by NCT and overestimation by rebound tonometer with TP as standard, whereas in eyes with corneal opacity, IOP measurements showed overestimation by NCT and underestimation by rebound tonometer. TP Avia was proved to be a useful instrument because of its smaller contact area and repeatability.