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Mydriasis is an eye condition that relates to your pupils, the black circles in your eyes.
Your pupils are responsible for controlling the amount of light that enters your eyes. In low-light environments, your pupils dilate (widen) to let more light in.
However, when your pupils remain dilated for an extended period, even when there’s bright light, you may have mydriasis.
Unlike miosis, in which your pupils constrict and become smaller, mydriasis refers to a continued enlargement of the pupils. Having dilated pupils can create discomfort and cause sensitivity to light or blurry vision.
If you have mydriasis, it is important to consult an eye care specialist or seek clinical help. While some mydriasis cases can be harmless, other cases may indicate an underlying health issue, such as a brain injury.
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Larger-than-normal pupil size may be benign or indicate an emergency problem. Seeking medical care will allow specialists to determine the cause of mydriasis and, if possible, next-step treatments.
Different types of medications can cause mydriasis. Here is a list of a few of those medications:
Doctors will use light and dark exposure to determine the problematic eye. A small pupil incapable of dilating in a dark room means no sympathetic response is present. However, a large pupil incapable of constricting in a light room means there’s an abnormality in the parasympathetic nervous system.
Illegal and illicit drugs like cocaine, ecstasy/MDMA, crystal methamphetamine (meth), or other amphetamines can result in mydriasis. LSD, a hallucinogenic drug, impacts the brain’s serotonin receptors and can also cause dilated pupils.
When a person consumes or abuses drugs, other symptoms, such as tachycardia (fast heart rate) and nausea, may be present.
Mydriasis can occur because of an underlying brain disease or traumatic brain injury.
If you experience pupillary dilation and a headache, it is important to seek medical help immediately. While the case may be benign, doctors will need to rule out any possible serious intracranial problem.
When there is unilateral pupil dilation, doctors may consider the following causes:
Adie’s tonic pupil is a rare neurological disorder that can cause one pupil to be larger than average and react slowly (if any reaction) to light.
In most cases, individuals with unilateral mydriasis are benign cases. These episodes may have occurred because of exposure to a topical mydriatic agent (drug).
However, benign episodic unilateral mydriasis (BEUM) may happen because of the impact caused by high levels of stress and anxiety. Evidence showing the association between these physiological responses and BEUM is growing.
If you experience accidental eye trauma, e.g., basketball injury, specific eye muscles can become damaged. For example, injury to the iris sphincter muscle (a muscle that helps with pupil constriction) could lead to mydriasis.
To determine the actual cause of mydriasis, an eye care specialist will ask for a complete history of your health and possible exposures to drugs, etc.
Anisocoria (unequal size of the pupils) can occur in up to 18% of people in specific lighting environments.
Symptoms of mydriasis can vary from one person to the next. The underlying cause of mydriasis will influence what symptoms will appear.
Nonetheless, when a person has mydriasis, she/he may experience:
Because mydriasis could indicate a serious, underlying health problem, complications may arise.
For example, if you experience unilateral mydriasis with a headache, doctors may suspect a brain injury like a stroke.
However, if you do not receive proper treatment in time, you may suffer long-term consequences, including:
Additionally, because of increased sensitivity to light, you may experience headaches or migraines more often.
You should visit your doctor or optometrist when you notice that your eyes remain dilated, often in bright settings. If you also see that one pupil is bigger than the other for an extended period, you should book an appointment.
When you do this, your healthcare specialist can review your individual case and help determine the underlying cause of the problem.
If you notice that your eyes frequently stay dilated even when in a bright environment, make an appointment to see your doctor or optometrist.
It is also important to see your eye specialist if you notice that one pupil appears larger than the other for a long time. They can help you determine the underlying cause of abnormally appearing pupils.
Your doctor will look over your symptoms and entire medical history. You should expect to list any medications or drugs that you’re taking. If you have suffered an injury to the eye, it’ll be important to share that information.
Also, your doctor will have you perform a visual acuity test. Visual acuity refers to how sharp or clear your vision is. Furthermore, you may undergo an ocular motility test (to evaluate proper eye muscle functioning) and a blood test as well.
Lastly, in suspected brain injury cases, your doctor may order neuroimaging scans. These images will help rule out any serious health concerns like a stroke.
Treatment for mydriasis will depend on the cause of the eye condition.
Because the affected eye(s) will increase your sensitivity to light, your doctor may prescribe opaque contact lenses or light-sensitive sunglasses. Surgery may also be an option.
Before proper treatment can occur, the doctor must perform the correct diagnosis.
If you have dilated pupils, there are a few steps you could take to manage the condition:
Avoid reading books or magazines up close. This can also result in blurred vision.
Bensinger, Richard E. “Is There a Cure for Mydriasis (Dilated Pupils)?” American Academy of Ophthalmology, 12 Mar. 2018, www.aao.org/eye-health/ask-ophthalmologist-q/is-there-cure-mydriasis-dilated-pupils.
Jacobson, Daniel M. “Benign Episodic Unilateral Mydriasis: Clinical Characteristics.” Ophthamology , American Academy of Ophthamology , 1 Nov. 1995, www.aaojournal.org/article/S0161-6420(95)30818-4/pdf.
Ma, Mina, and Jessica Liao. Unilateral Mydriasis: Emergent or Benign, UCLA Healthcare, 2017, proceedings.med.ucla.edu/wp-content/uploads/2018/02/Unilateral-Mydriasis-A170922MM-edited-BLM.pdf.
Roos, Jonathan. “Episodic Anisocoria and Anxiety.” Ophthamology - Letter to the Editor, AAO, 1 July 2008, www.aaojournal.org/article/S0161-6420(08)00194-2/fulltext.
Softing Hataye, Alaina L. “Eye Dilation: Necessary with Every Eye Exam?” Mayo Clinic, Mayo Foundation for Medical Education and Research, 31 Dec. 2019, www.mayoclinic.org/tests-procedures/eye-exam/expert-answers/eye-dilation/faq-20057882.
Witten, Nash A K, and Peter J Di Rocco. “The ‘Blown Pupil’: Imminent Death or Harmless Contamination?” Hawai'i Journal of Health & Social Welfare, University Clinical, Education & Research Associate (UCERA), Oct. 2019, www.ncbi.nlm.nih.gov/pmc/articles/PMC6787397/.