Fig. 3. Pupillograms of right and left pupil after treating the right eye with thymoxamine, which blocks the adrenergic input to the eye, and thus makes the pupil smaller. Note that dimmer light stimuli produce smaller but equal contractions of the right and left pupil, as evidenced by the lack of a changing anisocoria during the pupil contraction (left). At brighter light stimuli, the contractions are greater, and as the smaller pupil becomes limited by mechanical constraints, it does not contract as much as the untreated pupil at the peak of contraction, resulting in a decreasing anisocoria (center). At the brightest stimulus light, the smaller pupil is even more limited in its contraction, resulting in a larger reduction in anisocoria (right). The straight line below each anisocoria tracing represents a level of zero anisocoria.