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I Jalbert, E Papas, DF Sweeney, F Stapleton; Instrument, Diurnal, and Day to Day Repeatability of In Vivo Measurements of the Central Human Cornea Using slit Scanning Confocal Microscopy and Modified Optical Pachometry . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1713.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the repeatability of confocal microscopy (CM) measurements of keratocyte density, corneal haze and corneal thickness and to compare the latter to those obtained using modified optical pachometry (OP). Methods: Slit scanning CM (Confoscan 2, Fortune Technologies, Virgona, Italy) and OP were used to examine the central cornea of one eye of 20 subjects. Keratocyte density was calculated using automated image analysis of CM images and stereology equations. Thickness and haze were obtained from the CM z-curve. Multiple readings were taken consecutively in the afternoon and repeated at the same time on another day, as well as prior to sleep, on waking, and one and four hours after waking. Results: Consecutive repeats, time of day and day did not significantly alter density, haze or epithelial thickness measurements (p≷0.05). Corneal thickness values increased on waking (repeated-measures ANOVA, p<0.05) but did not vary during consecutive repeats or from day to day. Coefficients of repeatability (COR) were derived by multiplying the within subject standard deviation by the appropriate t0.05(2),19=2.093 (Table). Coefficients of repeatability (COR) View OriginalDownload SlideView OriginalDownload Slide Repeatability was poorest in the anterior stroma for density and in the posterior stroma for haze. Conclusion: Whilst OP showed highest repeatability for measuring thickness, slit scanning CM offers rapid quantification of central corneal sublayer thickness, keratocyte density and stromal haze from a single measurement. The diurnal variation of thickness measurements can be solely attributed to changes in stromal thickness however these do not appear to significantly affect keratocyte density. This study did not attempt to establish the measurement accuracy, which remains largely uncharacterised.
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