Photorefractive spatial screening solitons are treated as rays using geomet
rical optics. The ray picture is transformed into a classical mechanics pic
ture, in which solitons move self-consistently as particles in a potential
created by the induced change in the refractive index. The Hamiltonian equa
tions of motion are integrated to yield trajectories that agree with the op
tical center-of-mass trajectories. The motion in the transverse plane is fo
und to be not central and the orbits are not closed, preventing the spirali
ng of solitons.