In this case, mydriasis was considered to result from phenylephrine/lidocaine spray which was used to provide topical anaesthesia to the airway. Unilateral mydriasis, while unusual, may be seen during general anaesthesia and requires thorough knowledge of autonomic nerve pathways and pharmacology of the eye for correct diagnosis. Two muscles control the size of the pupil. The standard pupil size ranges between 2 millimeters (mm) and 8 mm, depending on the lighting. ![]() Drugs can produce mydriasis either by stimulation of the sympathetic innervation of the dilator pupillae or by inhibition of the parasympathetic innervation to the sphincter pupillae. It controls how much light enters the eye before it reaches the retina. Pharmacologic agents are a common cause of isolated unilateral or bilateral mydriasis. Consideration of these factors, the autonomic innervation of the eye, and an intraoperative "wake-up" test allowed satisfactory neurological assessment in this patient and surgery to proceed. A pupil is the round black circle in the center of the iris. Discussion: Several supplement mixes contain compounds with stimulant activity mimicking medications used for pupil dilation. The possible aetiology of the unilateral mydriasis includes the effects of anaesthetic agents, stellate ganglion block, impaired venous return from the head and neck, acute intracranial mass lesion or an haemorrhagic event, direct eye trauma, pre-existing medical or surgical conditions, and inadvertent direct deposition of alpha-adrenergic or anticholinergic agents in the eye. ‘Anisocoria (a unilateral dilated pupil) in critical care patients is a point of concern, which warrants a thorough examination and often, also, costly investigations to rule out a serious cause. I report finding a dilated right pupil (7 mm, nonreactive to light) after bronchoscopic tracheal intubation and induction of general anaesthesia in a frail, 74-yr-old woman with cervical subluxations and spinal cord impingement. In addition, the assessment of abnormal neurological findings is limited during general anaesthesia, and therefore requires special consideration. In addition, the assessment of abnormal neurological findings is limited during general anaesthesia, and therefore requires special consideration. Unilateral mydriasis is a disturbing finding during anaesthesia and may indicate serious neurological injury. On examination, the right pupil was dilated (mydriasis) (fig 1), direct and consensual light. Corrected visual acuity in the right eye was 0.8 and in the left eye was 1.0. ![]() She had no headache, eye pain, or double vision. It may also represent herniation of the uncus of the temporal lobe. Unilateral mydriasis is a disturbing finding during anaesthesia and may indicate serious neurological injury. A woman in her 50s presented to the emergency department with blurred vision and pupil asymmetry for three hours, which had started while she was pruning plants in her garden. The classic fixed and dilated 'blown pupil' is a unilateral phenomenon that may occur when a rapidly expanding intracranial mass, including blood from a hemorrhage, is compressing cranial nerve III.
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