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Assessing the posterior cornea in keratoconus: can we take a step forward?

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Session Details

Session Title: Presented Poster Session: Glaucoma and Imaging

Venue: Poster Village: Pod 3

First Author: : E.Kreps BELGIUM

Co Author(s): :    D. Gosling   D. Roels           

Abstract Details


To evaluate 2 methods of displaying the posterior corneal surface in keratoconus patients: the posterior radius of curvature (PRC) and the maximal point of posterior corneal elevation (posterior float or PF) in order to assess the potential use of PRC in assessing progression of keratoconus. For this use, we compared these 2 parameters with the maximal keratometric reading (Kmax) and the corneal thickness at the thinnest point (Pthin), common indices used in the evaluation of progression of keratoconus.


Ghent University Hospitals, Ghent, Belgium


We included 306 patients (306 eyes) with a diagnosis of keratoconus, using random selection of one eye when both were eligible. We searched our database of images on Pentacam (Oculus) from 2009 to present and included cases with scans of adequate quality, excluding grafts, post-crosslinking eyes and patients wearing rigid contact lenses when not removed more than 2 weeks prior to imaging. PRC is featured in the ABCD classification system available on Pentacam and represents the back radius of curvature taken from the 3.0 mm zone centered on the thinnest point. Statistical analysis was done using the Pearson's Correlation Coefficients.


PRC shows a stronger correlation with Pthin (r = 0.533) and Kmax (r = -0.407), as compared to the correlation of PF with Pthin (r = -0.478) and Kmax (r = 0.302). As expected, PRC and PF show a strong correlation (r = -0.853). PRC also correlates stronger to the radius of best-fit sphere (BFS) as compared to PF (r = 0.745 and r = -0.444).


In keratoconus patients, the posterior radius of curvature shows stronger correlation with other corneal parameters (minimal pachymetry and maximal keratometric readings) as compared to posterior float data. PRC is independent of the radius of BFS, which is subject to change over time. Using PRC instead of PF for measuring progression of keratoconus is thus an interesting hypothesis to further investigate.

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