Mydriasis happens when thepupilremains dilated (widened) and doesn’t respond to light changes in an environment.
It can happen due to an injury, medications, or psychological factors.
The pupil also dilates in response to factors such as touch, sound, and emotion.
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Fixed mydriasis in one eye can also be a red flag for severe brain injuries.
How Pupils Change Size
A pupil is the round black circle in the center of the iris.
It controls how much light enters the eye before it reaches the retina.
The standard pupil size ranges between 2 millimeters (mm) and 8 mm, depending on the lighting.
Two muscles control the size of the pupil.
What Is Miosis?
Traumatic Brain Injury
Mydriasis can occur in people withtraumatic brain injuries.
These often increase intracranial pressure, which can put pressure on and affect the eye system.
Medications
Mydriasis can also be a side effect of different medications.
While systemic medications cause bilateral mydriasis, direct ocular inoculation with topical medications can cause unilateral mydriasis.
Plants of the belladonna family and Jimson weed can also cause mydriasis.
Drug Use
Drugs can expand or shrink the eye muscles, causing mydriasis.
Substances such as cocaine increase serotonin level, which can lead to pupil dilatation.
LSD has a direct effect on serotonin receptors in the brain, which can also cause mydriasis.
Other drugs that have a similar side effect are crystal methamphetamine and ecstasy.
Increased Oxytocin Levels
Oxytocin is a hormone.
High levels of oxytocin can lead to mild or moderate mydriasis.
Cranial Nerve Neuropathy
Neuropathyis a disorder that impairs the ability to feel and move.
Pupil Dilation in Eye Exams
Not all causes of mydriasis are problematic.
Optometrists and ophthalmologists often use drops to dilate your pupils during an eye exam.
This allows them to examine theoptic nerveandretina.
Other causes, however, may be serious and require treatment.
Two types of ophthalmological eye drops are used during eye exams.
It often takes up to 30 minutes for a pupil to dilate after receiving the eye drops.
Your eye doctor cannot tell you how blurry your vision will be and for how long.
That depends on the key in of dilating eye drop used and how your eyes react to it.
When your eyes are dilated, they are often extremely sensitive to light.
Your vision becomes blurry and you will have trouble focusing on near objects.
Treatment
Treatment of mydriasis depends on its cause.
If medications are responsible, pupils usually return to normal once the medication effects wear off.
No treatment is needed in this case.
After a dilated eye exam, pupils may remain open for three to four hours, sometimes longer.
In 2023, the FDA approved Ryzumvi (phentolamine ophthalmic solution) to treat dilated pupils due to medication.
Your healthcare provider may prescribe Ryzumvi to constrict your pupils after an eye exam or procedure.
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