Pupil dilation, what s also referred to as mydriasis, happens when one of two muscle groups become activated, namely the iris sphincter (yes, that s what it s called) and the iris dilator. The sphincter response is triggered by the parasympathetic nervous system (what regulates our autonomic bodily processes when we re at rest), and the dilator by the sympathetic nervous symptom (what controls physiological responses requiring a quick response в like fight-or-flight). Needless to say, psychotropic drugs can have a profound effect on both of these systems. Depending on the type of drug taken, therefore, either muscle group can become engaged. Essentially, if a drug can trigger a parasympathetic or sympathetic response, there s a good chance that it will also impact on pupil dilation.
Specifically, mydriasis can be caused by stimulants and any drug that influences the adrenal glands в what can trigger certain parasympathetic responses. For example, drugs like MDMA, ecstasy, cocaine, amphetamines, and some antidepressants (like SSRIs) can increase serotonin levels in the brain в a crucial neurotransmitter that regulates mood, including feelings of happiness and well-being. Serotonin agonizes to the 5-HT2A receptors in the brain в what has the downstream effect of triggering the mydriasis response, and in some cases, psychedelic episodes. Consequently, mydriasis also occurs in people who take serotonin-inducing psychedelics like LSD, mescaline, and psilocybin.
Drugs that trigger the release of dopamine, a related neurotransmitter, can also induce mydriasis. Marijuana is a good example. Dopamine cause pupils to dilate by exciting the adrenergic receptors, what in turn increases adrenaline (which the autonomic nervous system is sensitive to).
You look in the mirror and notice that the dark circles in the middle of your are bigger than usual. What\’s going on? Those dark circles are your pupils, the openings that let light enter your eye so you can see. Muscles in the colored part of your, called the iris, control your pupil size. Your pupils get bigger or smaller, depending on the amount of light around you.
In low light, your pupils open up, or dilate, to let in more light. When itвs bright, they get smaller, or constrict, to let in less light. Sometimes your pupils can dilate without any change in the light. The medical term for it is mydriasis. Medicines, injuries, and diseases can all cause this eye condition. A few medicines can affect the muscles that control your pupils and prevent them from getting smaller when light shines in. These meds include: (Atropen), which treats problems with rhythm, issues, and some types of poisoning, like diphenhydramine, like and anti- medicines such as Parkinson\’s medications such as ( ) and -levodopa ( like amitriptyline ( ) and ( (, Myobloc) Anti- drugs, such as ( ) and topiramate ( Dilated pupils are one sign that someone has used, such as: These drugs affect the muscle that widens the pupil, slowing how it reacts to light.
So even in a bright room, the stay dilated. Withdrawal from these drugs can also make the pupils stay open wide. Pressure that builds inside your after a head injury, or tumor can damage the muscles in your iris that normally make your pupils open and close. One or both of your pupils can become fixed in the dilated position and canвt react to light. If that happens, you should see a doctor right away. If you\’ve had a, your doctor or nurse might shine a light into your during the exam to see if your pupils get smaller.