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Omar Shakir, sandeep Grover; Comparison of Corneal Topography Performed by Orbscan II and CASIA Cornea/Anterior Segment Swept Source Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3515.
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© ARVO (1962-2015); The Authors (2016-present)
Orbscan II (Bausch & Lomb, Rochester, NY) has been one of the gold standard methods of measuring corneal topography. The advancement of Optical Coherence Tomography (OCT) has led to its use in all parts of the eye, including the anterior segment. Recently introduced CASIA Swept Source OCT (Tomey, Tokyo, Japan) has the ability to evaluate corneal curvature and obtain corneal topography. A comparison of SS-OCT against the gold standard measurement in normal patients for corneal topography is necessary and is the purpose of our study.
45 eyes of 25 patients were included in this study. Patients were examined and found to have no clinical evidence of corneal disease other than refractive error between -6.00 diopters and +4.00 diopters. Astigmatic corneas were included. Screening examinations were performed by a single ophthalmologist. Topography was obtained on the same day. The first scan was obtained on the Tomey SS-1000 CASIA and the second scan was performed on the Orbscan II Corneal Topographer. The corneal topography 4 map mode was selected for analysis on the Tomey SS-1000 CASIA because it most closely parallels the 4 map presentation from Orbscan II. Values for steep keratometric value, flat keratometric value, cylinder value, and steep axis of cylinder were compared. Correlation coefficients and two-tailed T-test p-values were compared.
The difference between steep axis on the two machines was found to be 0.87 diopters (p-value 0.27). The difference between flat axis was found to be 0.77 diopters (p-value 0.59). The difference in cylinder was 0.4 diopters (p-value 0.64). And the difference in axis was found to be 14.7 degrees (p-value 0.86). All p-values were insignificant. Correlation coefficient was 0.95, 0.97, 0.93, and 0.86 respectively.
The Tomey CASIA SS-1000 Swept Source OCT can be used for corneal topography analysis in normal patients with similar results as the Orbscan II. Our results indicate that the CASIA SS-1000 can be used reliably in normal patients to obtain corneal topography. Further studies could include the use of Swept Source OCT in pathologic patients such as keratoconus. Also further comparison of normal patients with Oculus Pentacam (Wetzlar, Germany) would be of use since it is considered another gold standard of corneal topography.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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