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Michela Fresina, Giorgio O. Bravetti, Chiara Basiricò, Emilio C. Campos; Measurement Of Central Corneal Thickness: A Comparison Between Oct- Visante And Specular Microscope. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4184.
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To test the differences in measurements of central corneal thickness (CCT) obtained by Optical Coherent Tomograph (OCT) Visante and Specular Microscope (SM) in patients who underwent cataract surgery (phacoemulsification with intraocular lens implant-FACO+IOL).
Measurements of CCT using Zeiss OCT Visante 1000 (protocol "Global pachimetry map") and Topcon Specular Microscope SP-2000P obtained the day before (time 0), the next day (time 1) and one week after the operation (time 2) have been retrospectively evaluated in 50 patients (24 M and 26 F, mean age 75.82, standard deviation 8.4) operated on by the same surgeon. The number of patients suitable for inclusion in the study has been calculated using Power Analysis taking into account the standard deviations of the two different devices. The Describe-Comparative test has been used to obtain a graphical representation of data. A P value <0.05 has been considered statistically significant.
The difference between the CCT measurements obtained by the two devices was metrologically acceptable ("bias" 2.6%). The values obtained by Visante OCT were higher on average than those from Specular Microscope in all measurements (14.36±11.03 microns)(P <0.0001). Data from both devices show a statistically significant (P <0.0001) increase in CCT in all patients going from time 0 to time 1 (Visante OCT: 42,25 microns; SM: 35,60 microns) and a decrease from time 1 to 2 (Visante OCT: 36,09 microns; SM: 33,44 microns) with the Paired t-test and Compared Groups-1-way ANOVA test. No statistically significant differences were found in CCT from time 0 and time 2. A strong linear association between the two devices was present with the linear regression analysis. A Bland and Altman plot established a statistically significant coefficient of agreement between the CCT measurements obtained from the two instruments (0.14).
Values of CCT measurements by OCT Visante are always higher than those by Specular Microscope. Given the high rate of agreement between the two devices they can be used interchangeably in the measurement of CCT in clinical practice.
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