Influence of Corneal Visualization Scheimpflug Technology Tonometry on Intraocular Pressure

Abstract

Purpose: To investigate the effect of Corneal Visualization Scheimpflug Technology tonometry (CST) on intraocular pressure (IOP).

Design: Cohort study.

Participants: Patients with and without primary open-angle glaucoma (POAG) were included.

Methods: Intraocular pressure was measured using the Icare rebound tonometer (ICRT; Icare Finland Oy) and the biomechanically corrected IOP (bIOP) using the CST. Intraocular pressure was measured at baseline with ICRT, followed by a CST measurement in one eye with the fellow eye acting as a control. Icare measurements were repeated at 10 seconds and 1, 2, 4, 8, 15, 30, and 60 minutes in both eyes. The ratio of test eye IOP to fellow eye IOP was used to control for intrasubject variation.

Main outcome measures: Intraocular pressure change following Corneal Visualization Scheimflug Technology tonometry.

Results: Forty participants (mean age, 54.09 ± 20.08 years) were included comprising 20 patients with POAG and 20 patients with no ocular abnormalities other than cataract. Mean central corneal thickness was similar in those without POAG (547.4 ± 55.05 μm) and with POAG (520.22 ± 37.59 μm; P = 0.14). No significant change was found in IOP measured with the ICRT in the fellow eye versus the 1-hour period in either the healthy (P = 0.87) or POAG (P = 0.92) group. Significant changes were found in IOP after CST measurement for both healthy (P < 0.01) and glaucomatous (P < 0.01) eyes. After the CST measurement, the IOP reduced continuously from a mean of 13.75 mmHg to 10.84 mmHg at 4 minutes for healthy eyes and from 13.28 mmHg to 11.11 mmHg at 8 minutes for glaucomatous eyes before approaching (83% for healthy eyes and 92% POAG eyes) the pre-CST measurement at 1 hour.

Conclusions: Corneal Visualization Scheimpflug Technology tonometry causes a significant reduction in IOP in both glaucomatous and healthy eyes that lasts for at least 1 hour afterward.

Keywords: Biomechanics; CCT, central corneal thickness; CST; CST, Corneal Visualization Scheimpflug Technology tonometry; GAT, Goldmann applanation tonometry; Glaucoma; ICRT, Icare rebound tonometer; IOP, intraocular pressure; Intraocular pressure; POAG, primary open-angle glaucoma; bIOP, biomechanically corrected intraocular pressure.

Figure 1

Graph showing intraocular pressure (in millimeters of mercury) in treated and fellow eye in the healthy eye group after Corneal Visualization Scheimpflug Technology tonometry measurement.

Figure 2

Graph showing intraocular pressure (in millimeters of mercury) in treated and fellow eyes in the glaucoma group after Corneal Visualization Scheimpflug Technology tonometry measurement.

Figure 3

Graph showing the mean ratio at each time point of the intraocular pressure in the test eyes to that of the fellow eyes after Corneal Visualization Scheimpflug Technology tonometry measurement in healthy patients and those with primary open-angle glaucoma.