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J. Nemeth, B. Erdelyi; Alterations in the values and reproducibility of corneal topographic measurements during the inter–blink period . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2873.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To observe the effect of the post–blink interval on the values and reproducibility of corneal topographic measurements. Methods: Thirty ophthalmologically healthy subjects (13 men, 17 women; age 25.7+/– 5.6 years) were examined using a TMS–1 corneal topograph. Series of four photographs were taken at 5, 15, 30 and 60 seconds after a complete blink. The series was repeated three times in each individual. The main outcome measures were the values, standard deviation and reproducibility error of the parameters SRI (surface regularity index), SAI (surface asymmetry index), PVA (potential visual acuity), and the keratometric values (K1, K2). Results: SRI, SAI, and PVA changed significantly (p<0.05) during the one–minute pause in blinking, but reproducibility was unchanged. In contrast, although the keratometric values (K1 and K2) were stable during the period, their standard deviation and error of reproducibility increased significantly (p<0.04). The error may exceed 0.5 D of calculated keratometric power. Conclusions: Due to the tear–film dynamics and the pressure of the eyelids on the cornea, the ocular surface regularity is not constant during the inter–blink period. After blinking the surface regularity was found to decrease, and the keratometric measurement error to increase, at later times. This means that the measurement time–point is very important and should be optimised for reliable comparative results.
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