Comparison of the ICare rebound tonometer with goldmann applanation tonometer in refractive errors among patients attending tertiary eye centre in North East India

Abstract

Objective: To measure intraocular pressure (IOP) in patients with refractive errors and compare variations by means of ICare Rebound Tonometer (RT) and Goldmann Applanation Tonometer (GAT) and to also study the impact of central corneal thickness (CCT) on IOP measurements by these techniques. Materials and Methods: A total of 182 eyes from 182 subjects were included in this prospective cross sectional study. They were grouped as emmetropia (n=101), hypermetropia (n=11), low myopia (n=43) and high myopia (n=27). Each group underwent IOP measurements first by RT followed by GAT. CCT was assessed by ultrasound pachymetry. Subject preference for the method of IOP measurement was also assessed. Results: In all four groups, RT detected higher IOP readings than the GAT, significantly more in high myopia (RT-GAT=1.612.88mmHg, p=0.002) and low myopia (RT-GAT=1.162.72mmHg, p=0.004) as compared to emmetropia (RT-GAT =0.963.27mmHg, p=9.450) and hypermetropia (RT-GAT= 0.233.38 mmHg, p=0.398). CCT also showed positive relationship with RT especially in hypermetropia and emmetropia, the overestimation of IOP by 4.63mmHg (p=0.225) and 4.28mmHg (p=0.001) respectively. On the other hand the GAT underestimates IOP in thicker cornea. 52.75% patients preferred GAT as a measuring tool to RT (43.96%). Conclusions: IOP measurements by RT are overestimated as compared to GAT in both low and high myopia. CCT also has a positive relationship on the IOP measurements by RT. The GAT is therefore still the gold standard for IOP measurement but we cannot rule out the RT as a useful screening tool especially when we want to consider screening patients in peripheral care centres. Keywords: Goldmann applanation Tonometer, ICare rebound tonometer, Intraocular pressure, Refractive errors.