Measurement of angle Kappa with Orbscan II and Galilei G4: effect of accommodation

Abstract

Purpose: To measure angle kappa distance with Orbscan II and Galilei G4, and to evaluate possible variations in this value for different accommodation degrees.

Methods: Angle kappa was measured using the Orbscan II and the Galilei G4 in the right eye of 80 patients aged from 20 to 40 years. This value was measured three times per eye and per device, and the average was retained. Angle kappa was measured for far vision using the Orbscan II and the Galilei G4 in a random order for each subject. The Galilei G4 was used to measure angle kappa as a function of accommodation, where the first measure started at +1 D and the vergence was changed until reaching -4 D, in 1 D steps. In both measures, the kappa distance was expressed in millimetres.

Results: At distance, the values of angle kappa were 0.43 ± 0.13 mm and 0.27 ± 0.15 mm measured with the Orbscan II and Galilei G4 systems respectively. Statistical significant differences were found (P < 0.01). With regard to the angle kappa values obtained as a function of accommodation, the values were 0.25 ± 0.15 mm, 0.26 ± 0.15 mm, 0.30 ± 0.20 mm, 0.27 ± 0.15 and 0.26 ± 0.15 mm, for +1 D, -1 D, -2 D, -3 D and -4 D respectively. No statistical significant differences were found among 0 D and the other vergences evaluated (P > 0.01).

Conclusions: For far vision, Orbscan II measured significantly higher angle kappa values than Galilei G4, the mean difference being 0.16 ± 0.08 mm. For different accommodation levels, the kappa distance did not change significantly.