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R. Kopito, C. Allouch, O. Touzeau, S.E. Scheer, V.M. Borderie, L. Laroche; Evaluation of the Irido-corneal Angle with the Orbscan II Device . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2694.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the accuracy and reproducibility of the irido-corneal angle measurements obtained by the Orbscan II device. Methods: We prospectively studied subjective refraction and biometry in 200 normal eyes including eyes with ametropia. The irido-corneal angle was correlated with the spherical equivalent and other biometric parameters (i.e., anterior chamber depth (ACD), axial length, lens thickness, and corneal diameter) obtained by Orbscan and ultrasonic biometry. For each eye two Orbscan measurements were successively recorded to calculate the reproducibility. The angle was analyzed in 8 locations using both the "plan" and "polynomial" reconstruction modes. Results: The reproducibility of the angle measurements was significantly better in the plan mode than in the polynomial mode (5.7% ± 4.7 versus 8.8% ± 8.2; p<0.001). Significant differences were found within each mode (50.3° ± 4.5° plane mode versus 42.9° ± 6.7° polynomial mode; p<0.001). The correlation of the angle measurements with the other biometric parameters, the spherical equivalent, and the patient parameters were greater for the plan mode than for the polynomial mode. The angle in the plan mode was significantly correlated with the ACD obtained by Orbscan (rs=0.79; p<0.001), the ACD obtained by ultrasonic biometry (rs=0.78; p<0.001), the lens thickness (rs=-0.57; p<0.001), the axial length (rs=0.45; p<0.001), and the corneal diameter (rs=0.17; p<0.009). Angle measurements in the plan mode were significantly correlated with the spherical equivalent (rs=-0.53; p<0.001). The angle values were higher in myopic eyes than in emmetropic and hyperopic eyes (respectively 52°, 48°, 42°; p<0.001). Angle measurements in the plan mode were significantly correlated with age (rs=-0.50; p<0.001). Conclusions: The irido-corneal angle analyzed with the Orbscan device in the plan mode provided high reproducibility and significantly correlated with the biometric parameters. The Orbscan II is the only non-contact method to evaluate the irido-corneal angle, and appears to be useful for clinical settings such as angle-screening.
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