[Differences in the measurement results of Goldmann applanation tonometry with and without fluorescein]

Abstract

Background: Goldmann applanation tonometry (GAT) is still the gold standard for measuring the intraocular pressure (IOP). Usually fluorescein eye drops are used additional to topical anesthesia to gain the best visualization results. The present study evaluated the differences in the results of GAT with and without fluorescein.

Methods: A total of 400 eyes of 200 patients without known glaucoma were enrolled in this study and randomized to two groups: group A (first measurement without, second measurement with fluorescein) and group B (first measurement with fluorescein, second without). All measurements were performed by the same examiner with the same slit lamp. Results were analyzed by Bland-Altman plots and Spearman's correlation test.

Results: The examined groups showed no significant differences regarding patient age, astigmatism or reason for consulting. In both groups performing GAT without the application of fluorescein led to significantly lower measurement results. The differences were 1.5 ± 1.7 mmHg SD in group A, 1.2 ± 1.6 mmHg SD in group B and 1.4 ± 1.65 mmHg SD for all eyes. The intraocular pressure (IOP) and the differences between the groups were independent of patient age, astigmatism, reason of consulting or IOP level. Both groups showed outliers up to 10 mmHg difference because of corneal edema.

Conclusions: Measurements from GAT without fluorescein differed significantly from measurements with fluorescein, independently of patient age, astigmatism, reason for consulting or IOP level. The mean difference of 1.4 mmHg may seem negligible in daily routine but can lead to serious consequences in borderline cases.