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To compare the accuracy and reproducibility of the orbscan pachymetry and ultrasonic pachymetry in the normal eye and in the penetrating keratoplasty eye.Pachymetric measurements were assessed in 50 eyes of 25 normal patients and 50 eyes of 48 patients who had undergone penetrating keratoplasty using both Orbscan II and ultrasonic pachymetry (Tomey SP-2000). For each eye, 2 successive measures were recorded with both instruments. For both devices, the default setting was used. Orbscan pachymetry maps were divided into 5 groups using a modification of Liu's classification.Orbscan pachymetry strongly correlated with ultrasonic pachymetry (rs = 0.91; p0.001). Ultrasonic pachymetry values and Orbscan pachymetry values showed no significant differences in the normal group (respectively, 557 microns +/- 36 and 555 microns +/- 34; p0.05). Ultrasonic pachymetry values and orbscan pachymetry values were significantly different in the penetrating keratoplasty group (respectively, 571 microns +/- 52 and 550 microns +/- 54; p0.001). The best value for the acoustic factor for Orbscan pachymetry in the penetrating keratoplasty group was 0.89. Ultrasonic pachymetry reproducibility and Orbscan pachymetry reproducibility were not significantly different (0.86% +/- 0.61 v. 0.67% +/- 0.63; p = 0.13 in the normal group; 1.22% +/- 0.81 v. 1.23% +/- 1.13; p = 0.92, in the penetrating keratoplasty group). Both pachymetry methods showed less reproducibility in the penetrating keratoplasty group than in the normal group (p0.02). Thinnest point localization was significantly different in both groups (p0.001). In 66% of the normal group, the thinnest point of the cornea was located in inferotemporal quadrant. This point was located at an average of 0.63 +/- 0.25 mm from the visual axis in the normal group and 1.60 +/- 0.81 mm in the penetrating keratoplasty group (p0.001). Whereas "Centered round" (40%) and "centered oval" (34%) were the most common patterns in the normal group, "decentered oval" (40%) and "irregular" (30%) were more frequent in the penetrating keratoplasty group (p0.001).Orbscan pachymetry strongly correlated with ultrasonic pachymetry. Reproducibility of both methods is excellent and not significantly different. Thinnest point localization and pachymetric map classification are significantly different in normal eyes and in penetrating keratoplasty eyes.

Objectif Analyser la variation de la refraction objective induite par la dilatationpupillaire pharmacologique dans une population « normale ». Materiels et Methodes Analyse prospective de la refraction objective obtenue a l’aide d’un auto-kerato-refractometre avant et apres dilatation pupillaire maximale obtenue par instillation de tropicamide et de neosynephrine. Les donnees refractives ont ete exprimees dans un espace dioptrique par 3 coordonnees cartesiennes (x, y, z) representant l’equivalent spherique et 2 cylindres croises de Jackson d’axes 0°/90° et 45°/135°. Resultats 44 yeux de 22 patients phaques âges en moyenne de 53 ans (de 18 a 80) ont ete inclus. L’astigmatisme moyen est de + 0,37D × 175,9° avant dilatation et de + 0,18D × 3,0° apres dilatation soit une variation vectorielle de +0,21D × 79,9°. Apres dilatation pupillaire, l’equivalent spherique se modifie significativement (hypermetropisation de 1,08D : − 0,22D vs + 0,86D p S > = 0,41 p = 0,003) contrairement aux variations du cylindre et de l’axe. Discussion Contrairement a la dilatation en ambiance scotopique qui entraine une myopisation (« myopie nocturne »), la dilatation pupillaire pharmacologique entraine essentiellement une hypermetropisation d’origine cristallinienne. Cette hypermetropisation semble liee a l’action cycloplegique du tropicamide. La dilatation pupillaire pharmacologique n’entraine pas de variation de l’astigmatisme total et de l’astigmatisme corneen anterieur. Conclusion La dilatation pupillaire pharmacologique modifie essentiellement l’equivalent spherique dans le sens d’une hypermetropisation sans modification de l’astigmatisme.