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J.T. Wilensky, R. Kapur, R. Anderson, D.P. Edward; Intra and Interobserver Reproducibility of Ultrasonic Corneal Pachymetry Measurements Using Two Instruments . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4865.
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Purpose:Corneal pachymetry has become an important clinical tool in the assessment of glaucoma risk. Ultrasonic pachymeters are the most common instruments used to measure corneal thickness in glaucoma patients. Precise corneal thickness measurements depend on correct placement of the probe on the cornea. Little is known about the intra and interobserver variability in measurements with ultrasonic pachymeters. Furthermore, multiple pachymeters are currently available on the market. It is however unclear if pachymeter measurements between devices currently available are comparable. This study was conducted to determine the reproducibility of corneal pachymetry measurements obtained by one observer and between different observers. In addition, we compared corneal thickness measured by two ultrasonic pachymeters from different manufacturers. Intra– and interobserver reproducibility and between machines was calculated by intraclass correlation coefficient (ICC) for each eye. Methods: Three ophthalmic technicians who were familiar with the device used a single pachymeter to measure corneal thickness . Each of the three technicians measured the corneal thickness of both eyes of each volunteer (N=35) three separate times on a single day during a one week period using the same pachymeter. One month later, one of these technicians obtained three additional measurements at separate times during a single day using a different brand ultrasonic pachymeter on the same group of volunteers. Results: There was excellent reproducibility of the thickness measurements by a single observer, between observers and between pachymeters. ICC ranges of the intra– and interobserver measurements were 0.95–0.96 and 0.96–0.99 respecctively. The maximum standard deviation for a single observer was 5 microns and the maximum difference between mean corneal thickness values among observers was less than 5 microns. Good ICC was obtained with measurements using the 2 different brands of pachymeters (ICC range 0.90–.95) and the maximum difference in readings between pachymeters was less than 2 microns. Conclusions: Corneal thickness measurements obtained with an ultrasonic pachymeter shows excellent reproducibility when measured by the same operator, and between different operators. In addition, the pachymtery measurements between two brands of ultrasonic pachymeters were also consistent and reproducible.
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