Correcting applanation tonometer surface prism accuracy and correlation to biomechanical errors: a multicentre randomised clinical trial
Session Details
Session Title: Presented Poster Session: Glaucoma I
Venue: Poster Village: Pod 3
First Author: : S.McCafferty USA
Co Author(s): : J. Levine A. McColgin
Abstract Details
Purpose:
Clinically evaluate IOP measurements taken with a Goldmann applanation tonometer (GAT) prism and a modified surface Goldmann prism examining measurement differences correlated to central corneal thickness (CCT) and corneal hysteresis (CH) values.
Setting:
Prospective, open-label, randomised, controlled, multi-centre reference device accuracy analysis
Methods:
A GAT and a modified surface GAT prism measured IOP on 243 unique eyes. The study design and methodology complied with International Standard Organisation (ISO) tonometer evaluation guidelines, except the inclusion of thin (<500µm) and thick (>600µm) corneas. All eyes were randomised to IOP measurement by one of 5 standard Goldmann prisms and 5 modified prisms. Pressures were measured by 6 investigators, 2 times with each prism for a total of 1936 IOP measurements. Analysis included a multiple linear regression including CCT and CH correlation.
Results:
The difference in IOP measurements of the standard and modified Goldmann prisms correlated well to CCT particularly in thin (<500µm) and thick (>600µm) corneas (R2=0.404, p=0.007). Corneal hysteresis (CH) also significantly correlated to the difference in prism measurements (R2=0.125, p=0.039). There was no significant overall mean IOP bias between the two prisms (+0.43mmHg in modified, p=0.19).
Conclusions:
The paired IOP measurement difference between GAT and a modified surface Goldmann replacement prism indicated a statistically significant correlation to CCT and CH. A simple modified replacement prism for any Goldmann-type tonometer may significantly improve IOP measurement accuracy by minimising corneal biomechanical errors associated with CCT and CH.
Financial Disclosure:
... has significant investment interest in a company producing, developing or supplying product or procedure presented, ... research is funded, fully or partially, by a competing company