I'm trying to simulate light rays going through an eyepiece to characterize its magnification in function of the distance from the optical axis (image distortion). Attached is a figure showing the simulation console. Some lenses in the eyepiece are movable to correct for myopia/hypermetropia. When the object is exactly at the focal point (rays from a single point all exit parallel), magnification is easily calculated from the angle of exiting rays. HOWEVER, when the lens correct for myopia, the rays exiting from the eyepiece are not parallel, how can I calculate magnification in function of the distance from the optical axis (image distortion) in that case? Thanks a lot!