Validation of iCare IC200® rebound tonometry for intraocular pressure measurement

To validate the measurement of intraocular pressure (IOP) using rebound tonometry (RT) compared to Goldmann applanation tonometry (GAT).

We measured air puff tonometry (AT) with estimation of pachymetry, then IOP using GAT and RT in adult patients. We measured internal validity (agreement with Lin concordance coefficient-LCC, sensitivity and specificity for ocular hypertension (IOP threshold>21mmHg) and external validity (depending on pachymetry and body mass index) and determined the most comfortable method for the patients.

We included 341 eyes of 171 patients (73.2±10.7 years old, 52.1% men). Mean IOP was 16.5±4.7mmHg for RT and 16.2±4.1mmHg for GAT. Mean IOP difference between RT and GAT was 0.31±1.43mmHg; LCC was 0.95 (0.94 to 0.96, P=0.005). The prevalence of eyes with an IOP measurement >21mmHg was 15.5% for RT and 12.6% for GAT. Sensitivity and specificity of RT were 86% (71.1% to 94.7%) and 94.6% (91.4% to 96.9%) respectively. Depending on pachymetry, LCC was 0.98 (0.98 to 0.99), 0.94 (0.91 to 0.97), 0.94 (0.92 to 0.96), and 0.88 (0.83 to 0.93) between RT and GAT, respectively for the 4 pachymetry groups (<500, 500-520, 520-560, >560microm). Results were similar across BMI ranges (<25, 25-30, 30-35, >35). The most comfortable method was RT for 87% of patients.

RT is highly reliable in adult IOP measurement and independent of pachymetry and BMI.