Postganglionic right Horner syndrome

(A) In the light, there is mild anisocoria, with the right pupil being smaller than the left pupil. There is also decreased palpebral fissure on the right.
(B) In the dark, the right pupil does not dilate well.
(C) After instillation of 1% hydroxyamphetamine in both eyes, only the left pupil dilates, suggesting a lesion involving the postganglionic oculosympathetic pathways (third-order Horner syndrome).