A function of the body that happens automatically without a thought, was considered to be impossible to replicate at will. Yet a 23-year-old student in Germany can shrink and enlarge his pupils on ...

Medically reviewed by Johnstone M. Kim, MD Key Takeaways The pupil controls how much light enters the eye, allowing for clear ...

Opioids can cause small pupils, but so can several other things. If you’re concerned that someone is misusing opioids, there are other signs to look for. Share on Pinterest Chelsea Victoria/Stocksy ...

New pupillometry research reveals how post-traumatic stress disorder (PTSD) may affect both branches of the autonomic nervous system. By measuring how someone's pupils dilate and constrict in response ...

Drug addiction can often be spotted just by the appearance of the individual’s eyes. Of course there are several other physical changes that can give away the fact that someone is struggling with ...

The iris is a structure behind the transparent cornea of the eye. It has a circular opening called the pupil that changes size in response to the light level. Your pupils are usually the same size as ...

Experimenting with mice, neuroscientists at Johns Hopkins Medicine report new evidence that the eye's iris in many lower mammals directly senses light and causes the pupil to constrict without ...

The eyes are a window into our autonomic nervous system. Everyone's unique personal history and autobiographical experiences have the power to influence how and when the sympathetic nervous system ...