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First Author: R.Correa USA
Co Author(s): W. Trattler R. Ambrosio Jr R. Santos I. Ramos B. Valbom A. Canedo
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To report the repeatability of the Rotating Scheimpflug Camera with Pentacam HR, assessing anterior and posterior corneal surfaces and thickness measurements in keratoconic eyes.
Center for Excellence in Eye Care, Miami, USA. Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil.
In this prospective study, 10 eyes randomly selected from 10 patients with moderate to advanced keratoconus had 5 successive measurements taken by the same observer using the Pentacam HR. Repeatability was assessed for: flat (k1), steep (k2) and mean (Km) keratometers from anterior and posterior curvatures; maximal keratometer (Kmax); best fit spheres (BFS) of 8mm in diameter centered on thinnest point (TP) and corneal thickness at pupil center, apex (central cornea thickness, CCT) and TP. Km values from a circular area centered on Kmax with zone diameter of 1, 2, 3mm and Ambrosios Relational Thickness minimum, maximum and average (ARTmin, max, avg) were included. The average and standard deviation (SD) of the 5 measurements were calculated for each parameter for each eye. The average of the variables and the average of the SD of each parameter were calculated for all the 10 eyes (repeatability for the population). Coefficient of repeatability (CR; 1.96 * average of SD); and coefficient of variation (CV; ratio of SD over the average of the measurements) were also calculated.
The population mean age was 31 ḟ14.9 years. Average Kmax was 53.58 ḟ5.95D (46.8 67.2D) and average TP was 475.6 ḟ48.1?m. Kmax values had CR of 0.625D and CV of 0.595%. Km in 3mm and front Km had CR of 0.361D and 0.282D, and CV of 0.361% and 0.301%, respectively. Back Km had CR of 0.078D and CV of 0.565%. Elevation data, front and back BFS at TP, had CV of 5.7% and 5.4%, respectively.Among the thickness measurements analyzed, ART min, max and avg had CV of 7.665%, 5.315% and 3.852%, respectively. Pachymetry at the apex, pupil center and thinnest point provided CV of 0.711%, 0.734% and 0.814%, respectively.
Pentacam HR was found to be very precise elevated based system in terms of repeatability across the measurements assessed in keratoconic eyes. Advanced keratoconic eyes seem to have less repeatable measurements than mild to moderate keratoconic eyes. The high degree of repeatability has a potencial to detect changes on the anterior and posterior surfaces of the cornea allowing the experts to detect the progression of the disease.
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