• In the SPE model we propose, sensitivity (S) to deprivation results in changes that may be either plastic (P) (permanent) or elastic (E) (temporary). The effects of various levels (hours per day) of monocular occlusion in amblyopic children are measured as the change in visual acuity in each eye. At the patching level extremes (12 or more hours per day, zero hours per day) the effects on visual acuity in the two eyes are reciprocal, but nearly equal (symmetrical). At intermediate levels of occlusion, the asymmetries in effects necessary for successful occlusion can be demonstrated. Additional measurements of SPE parameters in children may allow for the determination of occlusion dose response whereby the risks of occlusion amblyopia and interference with binocularity may be avoided.
Jastrzebski GB, Hoyt CS, Marg E. Stimulus Deprivation Amblyopia in ChildrenSensitivity, Plasticity, and Elasticity (SPE). Arch Ophthalmol. 1984;102(7):1030-1034. doi:10.1001/archopht.1984.01040030832027