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International values of corneal elevation in normal subjects by rotating Scheimpflug camera
Matthew T Feng1, Michael W Belin, Renato Ambrósio
1Department of Ophthalmology and Vision Science, University of Arizona, Tucson, Arizona, USA.
Purpose:
To examine whether clinically significant differences exist in corneal elevation data from a sampling of countries worldwide.
Setting:
International multicenter.
Design:
Evaluation of diagnostic test or technology.
Methods:
One randomly selected eye of normal adults from 8 countries spanning 6 continents was examined using the Pentacam Eye Scanner. Anterior and posterior elevations were measured at the apex and thinnest point. Differences between countries were assessed by Kruskal-Wallis. Normative thresholds were defined according to the Tukey method.
Results:
The study examined 1 eye of 555 patients. Median elevations were similar across countries. Upper limits of normal for collective international data were 3.5 μm, 6.0 μm, 7.5 μm, and 13.5 μm at the anterior apex, anterior thinnest point, posterior apex, and posterior thinnest point, respectively. These and country-specific thresholds were similar to normal values from previous data; however, country-specific thresholds flagged additional eyes in China, Egypt, and India. Those thresholds were 4.5 μm at the anterior thinnest point (China and Egypt), 7.4 μm at the posterior apex (India), and 11.0 μm and 12.0 μm at the posterior thinnest point (China and Egypt, respectively).
Conclusions:
In general, international variations were clinically insignificant; thus, current screening guidelines maintained their applicability. Notable exceptions were China, Egypt, and India, where country-specific thresholds may better reflect the test populations and minimize potential false negative results from screening.
Financial Disclosure:
No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.
