Intraobserver reliability of contact pachymetry in children

BACKGROUND Central corneal thickness (CCT) is an important measurement in the treatment and management of pediatric glaucoma and potentially of refractive error, but data regarding reliability of CCT measurement in children are limited. The purpose of this study was to evaluate the reliability of CCT measurement with the use of handheld contact pachymetry in children. METHODS We conducted a multicenter intraobserver test retest reliability study of more than 3,400 healthy eyes in children aged from newborn to 17 years by using a handheld contact pachymeter (Pachmate DGH55; DGH Technology Inc, Exton, PA) in 2 clinical settings with the use of topical anesthesia in the office and with the patient under general anesthesia in a surgical facility. RESULTS The overall standard error of measurement, including only measurements with standard deviation <= 5 mu m, was 8 mu m; the corresponding coefficient of repeatability, or limits within which 95% of test retest differences fell, was +/-22.3 mu m. However, standard error of measurement increased as CCT increased, from 6.8 mu m for CCT less than 525 mu m, to 12.9 mu m for CCT 625 mu m and greater. The standard error of measurement including measurements with standard deviation >5 mu m was 10.5 mu m. Age, sex, race/ethnicity group, and examination setting did not influence the magnitude of test retest differences. CONCLUSIONS CCT measurement reliability in children via the Pachmate DGH55 handheld contact pachymeter is similar to that reported for adults. Because thicker CCT measurements are less reliable than thinner measurements, a second measure may be helpful when the first exceeds 575 mu m. Reliability is also improved by disregarding measurements with instrument-reported standard deviations >5 mu m.