Different Effects of Aging on Intraocular Pressures Measured by Three Different Tonometers

This study aimed to compare intraocular pressures (IOP) using different tonometers, Goldmann applanation (IOP(GAT)), non-contact (IOP(NCT)), and rebound (IOP(RBT)), and to assess the effects of aging and central corneal thickness (CCT) on the measurements. The IOP(GAT), IOP(NCT), IOP(RBT), mean patient age (65.1 ± 16.2 years), and CCT (521.7 ± 39.2 µm) were collected retrospectively from 1054 eyes. The differences among IOPs were compared by the paired t-test. Possible correlations between devices, age, and CCT were assessed by linear regression analyses. The effects of age and CCT on the IOP reading were assessed by mixed-effects regression models. The IOP(GAT) values were 2.4 and 1.4 mmHg higher than IOP(NCT) and IOP(RBT), respectively; the IOP(NCT) was 1.0 mmHg lower than IOP(RBT) (p < 0.0001 for all comparisons). The IOPs measured by each tonometer were highly correlated with each other (r = 0.81–0.90, t = 45.2–65.5). The linear regression analyses showed that age was negatively correlated with IOP(NCT) (r = −0.12, t = −4.0) and IOP(RBT) (r = −0.14, t = −4.5) but not IOP(GAT) (r = 0.00, t = −0.2); the CCT was positively correlated with IOP(GAT) (r = 0.13, t = 4.3), IOP(NCT) (r = 0.29, t = 9.8), and IOP(RBT) (r = 0.22, t = 7.2). The mixed-effect regression models showed significant negative correlations between age and IOP(NCT) (t = −2.6) and IOP(RBT) (t = −3.4), no correlation between age and IOP(GAT) (t = 0.2), and a significant positive correlation between CCT and the tonometers (t = 3.4–7.3). No differences between IOP(GAT) and IOP(RBT) were seen at the age of 38.8 years. CCT affects IOPs from all tonometers; age affects IOP(NCT) and IOP(RBT) in different degrees. IOP(RBT) tended to be higher than IOP(GAT) in young subjects, but this stabilized in middle age and became higher in older subjects.