[Sleep modifies anticholinergic mydriasis]

In sleep, the eyelids are closed and the pupils narrow. The pupil width indicates alertness and, if it is narrow, sleepiness. The deeper the sleep, the narrower the pupil: miosis during drowsiness, sleep, sedation and general anesthesia relies on reduced inhibition of the oculomotor nucleus and, even more, on reduced sympathetic tone (it is as sympatholysis that accounts for the miosis exerted by the famous "cocktail lytique" onto an iris whose sphincter is weakened from briskly elevated IOP in angle-closure glaucoma). For whatever reason a lack of sympathetic tone occurs, a poor response to anticholinergic mydriatics will be the consequence. This communication is concerned with children who received tropicamide, cyclopentolate or atropine for diagnostic pupil dilation and cycloplegia but, during subsequent sleep, exhibited an unsatisfactory mydriatic response that could be overcome by additional administration of phenylephrine. Thus, parasympatholytic mydriasis can be proven to be a function of the sympathetic tone. The pupil shrinks during deep sleep even after atropine. If the conditions of deep sleep, sedation or general anesthesia are present and mydriasis needs to be maintained, an additional administration of a sympathomimetic compound is mandatory.