Posted by: juliegriffey | April 15, 2011

Dilation: More than Meets the Eye

Our eyes naturally adjust to different light conditions.   Our nervous system detects environmental conditions and sends signals to the eye muscles to either grow or shrink the pupil.  In low light, the pupil grows to allow more light to enter the eye and shrinks in bright light to minimize the amount of light that enters the eyes.

Many people have experienced getting their eyes dilated by their eye doctor. Eye doctors use medications like tropicamide and phenylephrine to get the eyes to dilate.  Excessive pupil dilation is called mydrasis and the drugs that facilitate dilation are called mydratics.  These drugs block the receptors in the muscles of the eye, so the pupil can no longer respond to messages about lighting conditions.  The larger pupil allows the eye doctor to “see more clearly into the pupil to view the retina.”

Other conditions can cause the eyes to dilate unnaturally. Therefore, dilated eyes can be a clue for a physician making a diagnosis. Head trauma can damage the muscles controlling eye dilation which is why paramedics check eyes to determine whether the patient has had a head injury. Many drugs such as hallucinogenics, cocaine, marijuana, ecstasy and crystal meth and even prescription antidepressants will cause dilation. Ingesting chemical toxins and poisonous plants will also cause the eyes to dilate.  Dilated eyes can also indicate presence of a brain tumor.

Clearly, enlarged pupils can be more than meet the eye.

http://www.ehow.com/about_5042633_causes-dilated-pupils.html
http://www.strangequestions.com/question/577/What-causes-pupils-to-dilate.html
http://www.livestrong.com/article/140349-what-causes-eye-dilation/

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