Levi Symptom

LEVI SYMPTOM (Loewi) (Levi test, adrenaline reaction Loewi-Cords), described in 1908, is characterized by dilation of the pupil (mydriasis) upon local application of adrenaline to the eye; into the conjunctival sac of the eye, 2 drops of a 1%₀ solution of adrenaline are instilled 3 times over 5 minutes, after which the subject lies with eyes closed for 15 minutes; then the pupils are measured again every half hour until they return to normal. In healthy people, the dilation is minimal and quickly disappears; this symptom is specific for all conditions in which there is increased excitability of the sympathetic nervous system or that part of it which relates to the innervation of the m. dilatator pupillae (see Vegetative neuroses); the pupil dilates to maximum, and this dilation persists for many hours; general phenomena are minimal or absent altogether. Absence of mydriasis indicates increased parasympathetic tone or decreased excitability of the corresponding part of the n. sympathici. This symptom is found experimentally in dogs after removal of the pancreas, and in humans—in diabetes and in some cases of Basedow's disease, which speaks to the inhibitory influence of the pancreas on the body's sensitivity to adrenaline and the enhancing influence of the thyroid gland on it.