Nunzio Maresca1, Fabrizio Zeri2, Paolo Palumbo3, Antonio Calossi4. 1. Degree Course in Optics and Optometry, Faculty of Mathematics, Physics and Natural Sciences, Roma TRE University, Rome, Italy. Electronic address: nunziomaresca88@hotmail.com. 2. Degree Course in Optics and Optometry, Faculty of Mathematics, Physics and Natural Sciences, Roma TRE University, Rome, Italy. 3. Degree Course in Optics and Optometry, Faculty of Mathematics, Physics and Natural Sciences, Roma TRE University, Rome, Italy; Ospedale "Grassi" Roma, Italy. 4. Department of Physics (Optics and Optometry), University of Florence, Italy.
Abstract
PURPOSE: We compare the agreement and the reliability in measuring central corneal thickness (CCT) using two different technologies. METHOD: The right eyes of 35 healthy individuals who had a negative history of ophthalmic disease, or ocular surgery were examined. The CCT was determined sequentially with a rotating Scheimpflug camera (Sirius; CSO), and an ultrasound pachymeter (P-1; Takagi). For statistical analysis, we used the methods suggested by Bland and Altman. RESULTS: The mean values of CCT obtained from Sirius, and ultrasound were 537±28μm, and 550±35μm, respectively. There was a high correlation between Sirius and ultrasound (r=0.92; p<0.001), but the difference between the two measurements was statistically significant (t=-5.7; p<0.00001). The precision of Sirius and ultrasound were 9.4 and 15.9μm; repeatability 13.3 and 22.4μm, and coefficient of variation 0.9% and 1.5%, respectively. The intraclass correlation coefficient was 0.97 for Sirius and 0.95 for ultrasound. CONCLUSIONS: The average difference between corneal thickness measured with Sirius and ultrasound pachymetry was small but clinically significant. This means that the two instruments cannot be used interchangeably. Sirius showed precision and repeatability almost twice as much as ultrasound pachymetry. Confidence interval of 13.3μm for Sirius can show variations in corneal thickness with an uncertainty value lower than 2.5% in 95% of cases. The simplicity of use, the possibility to obtain pachymetric maps, and less invasiveness make this instrument potentially useful in contact lens practice.
PURPOSE: We compare the agreement and the reliability in measuring central corneal thickness (CCT) using two different technologies. METHOD: The right eyes of 35 healthy individuals who had a negative history of ophthalmic disease, or ocular surgery were examined. The CCT was determined sequentially with a rotating Scheimpflug camera (Sirius; CSO), and an ultrasound pachymeter (P-1; Takagi). For statistical analysis, we used the methods suggested by Bland and Altman. RESULTS: The mean values of CCT obtained from Sirius, and ultrasound were 537±28μm, and 550±35μm, respectively. There was a high correlation between Sirius and ultrasound (r=0.92; p<0.001), but the difference between the two measurements was statistically significant (t=-5.7; p<0.00001). The precision of Sirius and ultrasound were 9.4 and 15.9μm; repeatability 13.3 and 22.4μm, and coefficient of variation 0.9% and 1.5%, respectively. The intraclass correlation coefficient was 0.97 for Sirius and 0.95 for ultrasound. CONCLUSIONS: The average difference between corneal thickness measured with Sirius and ultrasound pachymetry was small but clinically significant. This means that the two instruments cannot be used interchangeably. Sirius showed precision and repeatability almost twice as much as ultrasound pachymetry. Confidence interval of 13.3μm for Sirius can show variations in corneal thickness with an uncertainty value lower than 2.5% in 95% of cases. The simplicity of use, the possibility to obtain pachymetric maps, and less invasiveness make this instrument potentially useful in contact lens practice.
Authors: Clara Ruiz-Belda; David P Piñero; Pedro Ruiz-Fortes; Roberto Soto-Negro; Myriam Moya; Rafael J Pérez-Cambrodí; Alberto Artola Journal: Graefes Arch Clin Exp Ophthalmol Date: 2015-07-15 Impact factor: 3.117
Authors: David Finis; Bernhard Ralla; Maria Karbe; Maria Borrelli; Stefan Schrader; Gerd Geerling Journal: J Ophthalmol Date: 2015-04-14 Impact factor: 1.909