ICareTM Tonometry: Reliability and Validity in Diabetic Patients

Purpose: Reliability and validity of ICareTM tonometer was evaluated for its accuracy on IOP measurements in diabetic patients and controls. Central and peripheral corneal pressures, within and between groups were compared.

Methods: This is a prospective study conducted from March 2015 to June 2015 in a tertiary hospital. Group 1 included central and peripheral IOP measurements in diabetics, Group 2 included central and peripheral IOP measurements in controls, Group 3 composed of central IOP measurements in diabetics and controls, and Group 4 was peripheral IOP measurements in diabetics and controls. Statistical analysis was performed by MedCalc software.

Results: Sixty eyes of 60 participants constituting 30 diabetics and 30 controls were recruited. Mean age in diabetics and controls was 52.63 (+/- 11.87) and 41.7 (+/- 16.53) years. Male to female ratio was 18 (60%) and 12 (40%) in diabetic group while 12 (40%) and 18 (60%) in control group. Mean central and peripheral IOP in diabetics was 15.20 (+/- 3.15) and 14.10 (+/- 3.95) mm of Hg. Mean central and peripheral IOP In controls was 13.97 (+/-2.70) and 13.73 (+/- 3.16) mm of Hg. Pearson coefficient (r) of -0.28, -0.19, 0.12 and 0.22 was found respectively for groups. Paired sample t test showed t values of 1.74, 0.45, -1.06 and -0.28 obtained respectively. Statistical significance was considered when p <0.05. Reliability of ICareTM tonometer was performed by calculating Cronbach’s alpha and intraclass correlation coefficient. Calculated Cronbach’s alpha was 0.44, 0.32, 0.22 and 0.37 respectively. Intraclass correlation coefficient of -0.27, -0.19, 0.12 and 0.22 as single measures were found respectively. ICareTM tonometer validity was determined by ROC curve and accuracy was calculated by AUC difference that revealed 0.23, 0.06, 0.14 and 0.35 respectively. Limits of agreement were evaluated by Bland-Altman difference plots.

Conclusion: ICareTM tonometry reliably measured ocular pressures in all groups with comparable values. Diabetic central pressures were negatively correlated with controls. Central and peripheral pressures showed slightly higher values in diabetics compared to controls.