Anatomical Axis, Visual Axis and Angle kappa

Anatomical Axis: The imaginary line which coming from the posterior pole of the eye ball and passes through center of the eyeball is called anatomical axis. Visual axis: The imaginary line which coming from the fovea centrallis of the eye ball and passes through nodal point of the eyeball is called visual axis. Angle kappa: the angle subtended between anatomical axis and visual axis is called angle kappa. Positive angle kappa: when fovea is slightly temporal to the posterior pole of the eye ball is called positive or normal angle kappa. Negative Angle kappa: when fovea is not at temporal side of the posterior pole is called negative angle kappa. if angle kappa is larger than the normal we feel psedoexotropia.