The near reflex is normal (light-near dissociation
Tonic pupil should be kepr in mind in eyes with light-near dissociation
. In this case report, bilateral tonic pupils and the possible mechanism which may cause this disorder were discussed.
Damage to this part of the pathway leads to light-near dissociation (where the near response is normal but the light response is defective).
Constriction of the pupil to near fixation but not to direct light is called light-near dissociation. This can be caused by viral infection, as in the case of Adie's tonic pupil, damage to the pre-tectal area (Parinaud's syndrome), or damage in the rostral midbrain (Argyll-Robertson pupil).
can be caused by severe loss of afferent light input to both eyes, caused by damage to the retina or optic nerve pathways, or samage at the tectum of the midbrain, causing loss of pretectal light input to the Edinger-Westphal nucleus (part of the parasympathetic chain of pupillary innervation).