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Erin M. Harvey, Joseph M. Miller, Michael Belin, Dawn H. Messer, J. Daniel Twelker; Agreement Between Retinomax K+ and Pentacam Measurements Of Anterior Corneal Astigmatism. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2821.
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To determine agreement between Retinomax K+ (Nikon, now manufactured by Right Mfg Co, ring keratoscope-based system) and Pentacam (Oculus, Inc, Scheimpflug camera-based system) measurements of anterior corneal astigmatism in 6-12th grade students.
Right eye Retinomax K+ and Pentacam anterior corneal astigmatism measurements were attempted on 76 6-12th grade students who attended one of two Tucson area schools at which the majority of students are members of a Native American Tribe (the Tohono O’odham) with a high prevalence of astigmatism. Retinomax measurements were obtained under cycloplegia (proparacaine, tropicamide, and cyclopentolate). Pentacam measurements were obtained prior to cycloplegia. If measurements were not of ideal quality, at least 1 additional attempt was made and the best measurement was used in analyses. The same examiner conducted all measurements.
Measurements of the right eye were obtained for all students using both instruments. The mean difference between Retinomax and Pentacam measurements of corneal astigmatism magnitude, axis, and curvature in the flattest and steepest meridian are summarized below for all subjects and for subjects with at least 1.00 D of right eye refractive astigmatism (per cycloplegic Retinomax). Corneal astigmatism agreement was within 0.50 D on 71/76 subjects (93%). Mean differences were significant for all measures, with the exception of curvature in the flattest meridian in the full sample, which near significance (p=0.06).
The Pentacam averaged slightly higher measurements of corneal astigmatism. Differences in corneal astigmatism measurements may be due in part to differences in measurement area between the two instruments. Differences in axis may be due in part to alignment error with the hand-held Retinomax, in comparison to the Pentacam which has a chin and forehead-rest. Although there were statistically significant differences between instrument measurements, differences were of minimal clinical significance.
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