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R. Kopito, O. Touzeau, C. Allouch, V.M. Borderie, L. Laroche; Analysis of the corneal thickness with Orbscan II and ultrasonic pachymeter . Invest. Ophthalmol. Vis. Sci. 2004;45(13):136.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To analyze the corneal thickness obtained by Orbscan and ultrasonic pachymeter. Methods: We prospectively studied the corneal thickness in 300 normal eyes of 150 patients with the Orbscan II (Bausch & Lomb) and Tomey SP–2000 ultrasonic pachymeter, including eyes with ametropia. We used default setting for both devices. Three central ultrasonic readings were averaged to give a single value. For each eye and for both devices two measurements were successively recorded to calculate the reproducibility. With the Orbscan we analyzed the central and peripheral (9 locations) pachymetry, as well as the thinnest point. The localization of the thinnest point according to the corneal apex was analyzed using cartesian coordinates. Results: Central pachymetric measurements of both eyes strongly correlated (rs= 0.98, p<0.001 ultrasonic pachymetry; rs= 0.97, p<0.001, Orbscan pachymetry). For the central pachymetric measurements both methods strongly correlated (rs= 0.97, p<0.001) and the precision of both methods was not significantly different (p=0.14). The difference between 2 successive measurements was approximatively 5 µm or 1%. The distance from the corneal thinnest point to the apex was 0.63 + 0.25 mm. The thinnest point was most commonly located in the inferotemporal quadrant (66%), followed by the superotemporal (24%), inferonasal (6%), and superonasal (4%) quadrants. The central pachymetry is not correlated with the subjective spherical equivalent but with the age (rs= 0.28; p<0.001). Conclusions: The corneal thickness analyzed with the ultrasonic pachymeter and Orbscan provided high reproducibility. There was a significant correlation between the results obtained by both techniques. Contrary to the ultrasonic pachymeters the Orbscan simultaneously measures several thousand points including the thinnest point and provides a colour–coded thickness map without physical contact.
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