To compare measurements from an Icare HOME rebound self-tonometer compared with those from a Goldmann applanation tonometer (GAT).
Materials and Methods:
A total of 130 subjects with suspected or confirmed glaucoma in our outpatient clinic were examined. Intraocular pressure (IOP) was measured using both an Icare HOME unit, by an ophthalmologist and by each participant, and again using a GAT, by an ophthalmologist. The Icare HOME self-measurement [Icare HOME performed by the patients (HOMEp)] was compared with those taken by the specialist using that unit and a GAT.
In total, 128 participants (98%, 128/130) were able to correctly conduct self-measurement. Of the 128 participants, the mean IOP was 12.2±2.8 mm Hg (range, 7 to 20 mm Hg) via GAT, 12.8±3.7 mm Hg (range, 6 to 24 mm Hg) with HOMEp and 13.1±3.8 mm Hg (range, 6 to 25 mm Hg) by Icare HOME specialist measurement [Icare HOME performed by the ophthalmologist (HOMEo)]. The mean difference between HOMEp and HOMEo was 0.21 mm Hg (P=0.068; paired t test). The mean difference between the HOMEp and GAT measurements was 0.70 mm Hg (P<0.001; paired t test), and between the HOMEo and GAT measurements it was 1.00 mm Hg (P<0.001; paired t test). The IOP difference between the HOMEp and GAT measurements was >3 mm Hg in 9.4% of cases (12/128), and >5 mm Hg in 2.3% of cases (3/128). A positive correlation was found between the central corneal thickness (CCT) and each of the 3 IOP values (HOMEp, HOMEo, and GAT: r=0.405, P<0.001; r=0.424, P<0.001; and r=0.400, P<0.001, respectively; Spearman correlation coefficient). The difference between HOMEp and GAT values was significantly increased with increasing CCT (P=0.024; Spearman correlation coefficient), indicating that a 10% increase in CCT predicted a 1.2% increase in the difference.
The Icare HOME tonometer is feasible for use in self-monitoring of IOP. Icare HOME tonometry measurements tend to overestimate IOP relative to GAT measurements.