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Abstract #27397 Published in IGR 12-4
Variability in the calibration error of the goldmann applanation tonometer
Choudhari NS; Jadhav V; George R; Vijaya LJournal of Glaucoma 2010;
PURPOSE: To investigate the variability in the measured calibration error with continued usage of Goldmann applanation tonometers (GATs) having unacceptable calibration error. METHODS: The study included 132 slit-lamp mounted Goldmann tonometers (Model AT 900 C/M; Haag-Streit, Switzerland). A single observer twice checked a randomly selected set of 25 instruments on 2 consecutive days to determine the intraobserver agreement in the measurement of GAT calibration error. The same observer prospectively checked all the instruments between 8 and 9 AM on any given day at all testing levels namely 0, 20, and 60 mm Hg and rechecked the faulty instruments (calibration error more than (plus or minus)2 mm Hg at any testing level) 2 times more on the same day between 12 noon and 1 PM and 4 and 5 PM. RESULTS: The single measures intraclass correlation coefficients for the intraobserver agreement at the 20 mm Hg testing level were 0.78 for positive error and 0.83 for negative error. Twenty-eight (21%) instruments were faulty at any testing level. Nineteen (14%) were faulty at the clinically most important 20 mm Hg testing level. The maximum observed variability in the positive and negative calibration error at any testing level was +4 and -23 mm Hg, respectively. Fifteen (53%) faulty instruments had high variability ((greater-than or equal to)2 mm Hg) in the calibration error at any testing level. CONCLUSIONS: The calibration error of faulty GATs can frequently have a high variability. One should avoid estimating the true intraocular pressure from a faulty GAT by instinct.
N. S. Choudhari.
Classification:
6.1.1 Devices, techniques (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)
