Pupil that responds to convergence but light reflex is absent -

Argyll Robeson pupil (ARP) . Here the pupil is slightly small in size and reaction to near reflex is present but light reflex is absent, i.e., there is light near dissociation (to remember, the acronym ARP may stand for 'accommodation reflex present'). Both pupils are involved and dilate poorly with mydriatics. It is caused by a lesion (usually neurosyphilis) in the region of tectum. OTHER ABNORMALITIES OF PUPILLARY REACTIONS 1. Amaurotic light reflex. It refers to the absenceof direct light reflex on the affected side (say right eye) and absence of consensual light reflex on the normal side (i.e., left eye). This indicates lesions of the optic nerve or retina on the affected side (i.e., right eye), leading to complete blindness. In diffuse illumination both pupils are of equal size. 2. Efferent pathway defect. Absence of both direct and consensual light reflex on the affected side (say right eye) and presence of both direct and consensual light reflex on the normal side (i.e., left eye) indicates efferent pathway defect (sphincter paralysis). Near reflex is also absent on the affected side. Its causes include: effect of parasympatholytic drugs (e.g., atropine, homatropine), internal ophthalmoplegia, and third nerve paralysis. 3. Wernicke's hemianopic pupil. It indicates lesion of the optic tract. In this condition light reflex (ipsilateral direct and contralateral consensual) is absent when light is thrown on the temporal half of the retina of the affected side and nasal half of the opposite side; while it is present when the light is thrown on the nasal half of the affected side and temporal half of the opposite side. 4. Marcus Gunn pupil. It is the paradoxical response of a pupil of light in the presence of a relative afferent pathway defect (RAPD). It is tested by swinging flash light test. For details see page 474. 5. The Adie's tonic pupil. In this condition reaction to light is absent and to near reflex is very slow and tonic. The affected pupil is larger (anisocoria). Its exact cause is not known. It is usually unilateral, associated with absent knee jerk and occurs more often in young women. Adie's pupil constricts with weak pilocarpine (0.125%) drops, while normal pupil does not. Ref :AK Khurana 4thE pg 294