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Joseph M Miller, Erin M Harvey, Michael W Belin; Anatomical Correlates of Increasing and Decreasing Keratometric Astigmatism in Astigmatic Native American Children. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1120.
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© ARVO (1962-2015); The Authors (2016-present)
To assess anatomical differences in eyes of children with decreasing and increasing keratometric astigmatism (DKA, IKA) compared to children with stable keratometric astigmatism (SKA).
Subjects are Native American children who participated in at least two eye exams. Keratometry and autorefraction (Retinomax K-Plus2, Nikon, Melville NY) were performed at both exams, corneal tomography (Pentacam, Oculus, Wetzlar Germany) was performed at only the second exam. Apical pachymetry and SimK radii of curvature were used to derive radial corneal thickness (RCT) at the 3.5mm pupil margin, and an eye model was developed to derive ELP (SEQ and Cyl). Multinomial logistic regressions on right eye data comparing the DKA and IKA groups to the SKA group were performed within each ocular measure at baseline and final exam, and change from first to final exams.
The sample of 317 children (xx DKA, xx IKA, xx SKA), ranging in age from xx to xx at baseline exam, were followed an average of 8 years. The Table summarizes findings by group, along with significant (p<0.05) findings (shaded).
These findings indicate that at the final exam, DKA and IKA exhibit similar corneal thickness rotational symmetry. The steeper and flatter meridian are closely aligned, and meridional differences in thickness are ~6 microns, or ~1% corneal thickness. It does not appear that the lens astigmatism differs between eyes showing DKA and IKA. While groups are similar at the final exam, we lack evidence that they were also similar at the first exam, as we did not have Pentacam data for the first observation. We hypothesize that external forces may remodel a relatively stable cornea over time. These findings suggest that the high prevalence of astigmatism in this population is not associated with the relative corneal thinning of keratoconus.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Table of Anatomical Characteristics of children exhibing decreasing or increasing astigmatism over time.
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