Effect of corneal thickness on the agreement between ultrasound and Orbscan II pachymetry

作者：Hashemi Hassan; Roshani Maryam; Mehravaran Shiva^*; Parsafar Hiva; Yazdani Kamran

来源：Journal of Cataract and Refractive Surgery, 2007, 33(10): 1694-1700.

DOI：10.1016/j.jcrs.2007.05.036

PURPOSE: To study the agreement between ultrasound (US) and Orbscan II (Bausch & Lomb) measurements with different ranges of central thickness in normal corneas.
SETTING: Noor Ophthalmology Research Center, Tehran, Iran.
METHODS: The central corneal thickness was measured first by the Orbscan II and then with a US pachymeter in 177 right eyes. Data were compared in 3 thickness groups: less than 500 mu m, 500 to 600 Lnn, and more than 600 pm. In all cases, uncorrected Orbscan II data were used. For each range, a correction factor was calculated through regression analysis, which was then used in a new set of analyses. To study the agreement between the 2 methods, the 95% limits of agreement (LoA) and intraclass correlations coefficients (ICC) were determined.
RESULTS: The mean interclevice difference was 2.7 +/- 16.9 (SD) in the less than 500 mu m group (P = .365), 21.3 +/- 3.1 in the 500 to 600 Lnn group (P = .0001), and 27.2 +/- 20.9 in the more than 600 Lnn group (P = .0001). No clinically acceptable LoA were found in any group. The application of regression equations to the Orbscan II readings improved the agreement in the less than 500 mu m group better than the other 2 groups. The ICC was 0.76, 0.61, and 0.43 in the less than 500 mu m, 500 to 600 mu m, and more than 600 mu mm groups, respectively.
CONCLUSIONS: The Orbscan corneal thickness readings had relatively lower validity than US measurements. The 2 devices should not be used interchangeably, especially when the validity of the measurement is vital. In patient screening for corneal surgery, it is advisable to recheck corneal thickness with a US pachymeter.

• 出版日期2007-10