Poor utility of intraocular pressure correction formulae in individual glaucoma and glaucoma suspect patients.

BACKGROUND

To compare Pascal dynamic contour tonometry (DCT) measurements with Goldmann applanation tonometry (GAT) readings after adjustment with correction formulae in a population of Caucasian glaucoma and glaucoma suspect patients.

DESIGN

Retrospective cross-sectional case series in a specialist glaucoma practice.

PARTICIPANTS

Consecutive glaucoma and glaucoma suspect Caucasian patients.

METHODS

Case notes review of the GAT and DCT intraocular pressure (IOP) measurements from patients who presented on a non-acute basis over a 30-month period. The GAT measurement was adjusted with six different correction formulae. Agreement between GAT IOP, adjusted GAT IOP and DCT IOP was evaluated with the Bland-Altman analysis.

MAIN OUTCOME MEASURES

Agreement between GAT IOP (both unadjusted and adjusted) and DCT IOP.

RESULTS

Data from 200 patients with a mean age of 58.4 (±12.7) years were analysed. The mean central corneal thickness was 554.8 (±36.9) µm and the mean corneal hysteresis was 9.8 (±1.9) mm Hg. Sixty five (32.5%) had confirmed glaucomatous optic neuropathy. GAT IOP demonstrated poor agreement with DCT IOP. GAT IOP was on average 2.1 mm Hg less than DCT IOP. None of the six correction formulae resulted in improved agreement with DCT IOP. General linear model analysis found no statistically significant measurement differences between the glaucoma and glaucoma suspect groups.

CONCLUSIONS

GAT demonstrated poor agreement with DCT, and agreement did not improve after adjustment with correction formulae. Our results suggest that correction formulae for GAT IOP are unsuitable to clinically approximate 'true' IOP in Caucasian glaucoma and glaucoma suspect patients.