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A.P. Maino; Safe or Sorry: Clinical Comparison Between Single Use Tonometry Devices and Goldmann Tonometer . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2188.
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Purpose: Goldmann applanation tonometry is performed on most patients who are examined in clinical practice. As a result, tonometer prisms are a potential vehicle for cross-infections. A way to avoid nosocomial infection via tonometer heads would be adopting single-use devices but little is known about their accuracy. This is the first study to evaluate the accuracy and performance of Goldmann tonometry using both sterile disposable prisms (Tonosafe) and silicone shields over the biprism tip (Tonoshield). Methods: Two investigators obtained 159 readings from 81 patients (Cohen’s kappa agreement between investigators=0.96). A Goldmann tonometer was used throughout the study and calibrated on a daily basis. Applanation tonometry was performed with the standard Goldmann procedure, with the disposable prism and with the silicone shield. To avoid measurement errors, we randomized the order of the devices tested. Mean values will be compared among groups using within-subjects ANOVA. As the test for heterogeneity of covariance was positive, we adopted a more conservative test, the Greenhouse-Geisser test and a correlation matrix was calculated. Results: Mean intraocular pressure readings (±SD) were 14.14 ± 4.50 (Goldmann), 14.13 ± 4.41 (prism) and 15.58 ± 4.96 (shield). The intraocular pressure readings obtained with the silicone shield were significantly higher than the one obtained with the other two methods. All three devices correlated well (Goldmann-prism: 0.913; Goldmann-shield: 0.797; prism-shield: 0.789). Conclusions: Although tonometry readings correlated well, an increased measured intraocular pressure resulted from using the silicone shield while there was close agreement between the other two devices. Therefore the study validates the use of disposable tonometer tips as a reliable and safer alternative to repeated chemical disinfection of the prism.
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