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Abstract #3455 Published in IGR 4-2
Effect of corneal thickness on intraocular pressure measurements with the pneumotonometer, Goldmann applanation tonometer, and Tono-Pen
Bhan A; Browning AC; Shah S; Hamilton R; Dave D; Dua HSInvestigative Ophthalmology and Visual Science 2002; 43: 1389-1392
PURPOSE: To compare intraocular pressure (IOP) measurements of the ocular blood flow (OBF) pneumotonometer, Goldmann applanation tonometer, and Tono-Pen in eyes with normal corneas of various thicknesses. METHODS: IOP was measured with an OBF pneumotonometer, Tono-Pen and Goldmann applanation tonometer in random order in 181 eyes with normal corneas. Central corneal thickness (CCT) was measured using an ultrasonic pachymeter after all IOP determinations had been made. Right and left eyes were analyzed separately for statistical purposes. RESULTS: With all instruments, IOP varied with CCT, even though the variation in IOP was large. Readings with the OBF pneumotonometer showed a mean increase in IOP with increasing CCT of 0.28 mmHg/10 μm, an increase of 0.23 mmHg/10 μm with the Goldmann tonometer, and of 0.10 mmHg/10 μm with the Tono-Pen. The OBF pneumotonometer consistently recorded comparatively higher IOPs than the other two instruments. CONCLUSIONS: The Tono-Pen is least affected by CCT when used to measure IOP in eyes with normal corneas. The OBF pneumotonometer appears to be more affected by variation in CCT than the Goldmann tonometer. This is contrary to expectations, based on the mechanism of measurement of IOP of the OBF pneumotonometer.
Dr. A. Bhan, Division of Ophthalmology and Visual Sciences, Queens Medical Centre, Derby Road, Nottingham NG7 2UH, UK
Classification:
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)
