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