Snap Shot Pupil Size Light Response Motor Interpretation Unilaterally dilated Sluggish or fixed Down and out (ptosis and paresis of medial rectus) IIIrd nerve compression secondary to tentorial compression Bilaterally dilated Sluggish or fixed Inadequate brain perfusion Unilaterally dilated or equal Cross-reactive Optic Nerve Injury Bilaterally constricted min OpiatesMetabolic EncephalopathyPontine lesion Unilaterally constricted Preserved Injured sympathetic Pathway Normal Normal Medial deviation (paralysis of lateral rectus) VIth nerve palsy