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

Kazunobu Sugihara,Masaki Tanito

doi:10.3390/jcm10184202

Abstract

This study aimed to compare intraocular pressures (IOP) using different tonometers, Goldmann applanation (IOPGAT), non-contact (IOPNCT), and rebound (IOPRBT), and to assess the effects of aging and central corneal thickness (CCT) on the measurements. The IOPGAT, IOPNCT, IOPRBT, 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 IOPGAT values were 2.4 and 1.4 mmHg higher than IOPNCT and IOPRBT, respectively; the IOPNCT was 1.0 mmHg lower than IOPRBT (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 IOPNCT (r = −0.12, t = −4.0) and IOPRBT (r = −0.14, t = −4.5) but not IOPGAT (r = 0.00, t = −0.2); the CCT was positively correlated with IOPGAT (r = 0.13, t = 4.3), IOPNCT (r = 0.29, t = 9.8), and IOPRBT (r = 0.22, t = 7.2). The mixed-effect regression models showed significant negative correlations between age and IOPNCT (t = −2.6) and IOPRBT (t = −3.4), no correlation between age and IOPGAT (t = 0.2), and a significant positive correlation between CCT and the tonometers (t = 3.4–7.3). No differences between IOPGAT and IOPRBT were seen at the age of 38.8 years. CCT affects IOPs from all tonometers; age affects IOPNCT and IOPRBT in different degrees. IOPRBT tended to be higher than IOPGAT in young subjects, but this stabilized in middle age and became higher in older subjects.

Highlights

Intraocular pressure (IOP) is the only known modifiable risk factor relevant to the treatment of glaucoma
The linear regression analyses showed that age was negatively correlated with IOPNCT (r = −0.12, t = −4.0) and IOPRBT (r = −0.14, t = −4.5) but not intraocular pressures (IOPs) using GAT (IOPGAT) (r = 0.00, t = −0.2); the central corneal thickness (CCT) was positively correlated with IOPGAT (r = 0.13, t = 4.3), IOPNCT (r = 0.29, t = 9.8), and IOPRBT (r = 0.22, t = 7.2)
IOPRBT tended to be higher than IOPGAT in young subjects, but this stabilized in middle age and became higher in older subjects

Summary

Introduction

Intraocular pressure (IOP) is the only known modifiable risk factor relevant to the treatment of glaucoma. Goldmann applanation tonometry (GAT) has been considered the “gold standard” for IOP measurement, its readings are affected by central corneal thickness (CCT), corneal curvature, the modulus of corneal elasticity, and tear film [1]. Noncontact tonometry (NCT) using air-puff pressure has several favorable characteristics, including no corneal contact and no requirement for local anesthesia, which facilitates convenient use [1]. Rebound tonometry (RBT) uses the impact rebound principle by launching a magnetized probe against the cornea using a solenoid; the speed of deceleration of probe is measured and converted into the IOP [2]. There is no need for an air puff, corneal anesthesia, and slit-lamp mounting, and the measurement skill enables affordable, quick, and repeated IOP measurements even in children and very old patients [3]. Most previous studies have assessed the CCT as a surrogate for explaining the measurement difference among tonometers [4,5,6,7,8,9,10,11,12,13,14,15,16]; other parameters that possibly affect IOP differences among tonometers have not been studied extensively

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