Definition
The mydriasis consists in the dilation of the pupil over 5 mm in diameter. In healthy people this event occurs physiologically due to the adaptation of the eye to darkness, or in the case of intense emotion. Pathological mydriasis, on the other hand, is observed in various conditions, including lesions of the eyeball or optic nerve, infectious states and intoxications.
One can have mydriasis in cavernous sinus thrombosis, in botulism, in acute angle-closure glaucoma and, occasionally, in the case of a skull base fracture and in cerebral haemorrhages. In the paralysis of the oculomotor nerve of vascular, tumor or traumatic origin, the pupil is perennially dilated. This sign is often associated with the absence of the pupillary reflex with light and with palpebral ptosis.
Mydriasis can also be caused by the use of drugs (eg amphetamines, cocaine, opioids, etc.), excessive alcohol consumption and withdrawal symptoms. Furthermore, it can be induced pharmacologically by instilling mydriatic substances in the eye, such as atropine, tropicamide and cyclopentolate, which are useful to the ophthalmologist to allow an adequate ocular examination.
Possible Causes * of Mydriasis
- Cardiac arrest
- Botulism
- Glaucoma
- Stroke
- Cerebral ischemia
- Reye syndrome
- Serotonin syndrome
