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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com obserVaTions in oPhThalmology Peer reviewed 80 • When administered to both eyes, if a preganglionic lesion is present, it causes (relative to the normal eye) rapid pupil constriction. • in a normal eye, administration of physostigmine (and pilocarpine, below) causes slow or delayed constriction of the pupil. Dilute pilocarpine (0.2%−1% solution) is a parasympathomimetic alkaloid that may be used to differentiate iris atrophy and other lesions of the iris, such as posterior synechia, from a lesion of the parasympathetic system. • animals with ocular parasympathetic dysfunction have rapid pupillary constriction following the administration of pilocarpine. • Those with iris atrophy demonstrate only partial constriction. • Posterior synechia results in no or minimal response to pilocarpine, but the patient should also have a dyscoric pupil and other signs of past or current inflammation. Table 3. Differential Diagnoses using the DaMNiTV schema cause locaT io N affecTeD affec T eD PuPil siZe Degenerative Intervertebral disk herniation Cervicothoracic cord Miosis Iris atrophy Iris Mydriasis a nomalous Hydrocephalus Cerebrum, thalamus Miosis or mydriasis Metabolic Hepatic encephalopathy Cerebrum, thalamus Miosis Nutritional Thiamine Cerebrum, brainstem Miosis or mydriasis Neoplastic Neoplasia Any Miosis or mydriasis Infectious/Infammatory Meningitis and encephalitis Intracranial structures, optic nerve Miosis or mydriasis Myelitis Cervicothoracic cord Miosis Uveitis Iris sphincter Miosis Middle ear infection Second order sympathetic neuron Miosis idiopathic Glaucoma Iris sphincter, CN II Mydriasis Sympathetic dysfunction Sympathetic pathway Miosis Dysautonomia Parasympathetic or sympathetic pathway Mydriasis Traumatic Head trauma CN II, cerebrum, thalamus, brainstem Miosis or mydriasis Brachial plexus avulsion Brachial plexus Miosis Jugular venipuncture Second order sympathetic neuron Miosis Aggressive deep ear fush Third order sympathetic neuron Miosis Neck trauma secondary to choke chain or strangulation Second order sympathetic neuron Miosis Vascular Ischemic brain disease Cerebrum, thalamus Miosis Fibrocartilagenous embolism Cervicothoracic cord Miosis