What are Pinpoint Pupils?
A pupil is a circular opening at the center of the iris (the colored part of the eye). Generally, pupils are equal in size and function to achieve clear vision.
Pupils constrict (decrease in size) in bright light to control how much light enters the eye. They dilate (expand) to allow maximum light when it's dark. This process is made possible by the iris sphincter and the iris dilator muscles.
The average adult pupil measures about 2 to 4 millimeters (mm) in diameter in bright light.1 In dim light, it expands to 4 to 8 mm. Pupil dilation and expansion are made possible by the iris sphincter and iris dilator muscles.
When the pupils are abnormally small and unresponsive to light, they're referred to as pinpoint pupils. This condition is known as miosis or myosis.
Myosis is not a disease; but may indicate an underlying problem.
6 Common Causes of Pinpoint Pupils
Several factors can cause constricted pupils. They include:.
1. Prescription or Illicit Drug Use
Prescription opioids are often used to relieve severe pain due to surgery, injury, or chronic illness such as cancer. However, some people use opioids as recreational drugs.
Opioid drugs include oxycodone, morphine, hydrocodone, codeine, heroin, and others. When taken in excess, they contract the iris sphincter muscles, making the pupils smaller and unresponsive to light.
Severe drug overdose will require emergency medical attention.
- Bloodshot or red eyes
- Cravings and sweating
- Nausea and vomiting
- Confusion or lack of alertness
- Slurred speech
- Difficulty breathing
Opioids are highly addictive, and an overdose can be fatal if left untreated. During opioid overdose, naloxone is often administered to block the action of opioids.
Depending on the addiction level, several treatment options are available:
- Medical detoxification (use of methadone to manage cravings)
- Behavioral counseling
- Support groups
- Recovery housing
2. Exposure to Toxins
According to the United Nations (UN) global review, about 200,000 people die annually due to pesticide poisoning.2 Some pesticides (organophosphates) and herbicides can cause pupils to constrict.
Nerve agents like sarin, soman, tabun, and VX are also known to cause pinpoint pupils.3
Although you may not notice exposure to toxins, pinpoint pupils are an excellent indicator for doctors.4
- Excessive saliva production
- Retching and vomiting
- Breathing difficulties
- Muscle weakness
- Rapid heartbeat
Any form of poisoning requires urgent medical care. If the person is unconscious or vomiting, make sure they're lying on their side with their head slightly tilted downwards. This will prevent choking on vomit. Treatment may include the following:
- Activated charcoal to prevent further absorption of the poison into the blood
- Antidotes, which reverse the effects of the poison
- Anti-seizure medications
- Sedatives to help the person relax in case of agitation
- Ventilators (breathing aids)
3. Anterior Uveitis (Eye Inflammation)
Anterior uveitis is the inflammation of the iris and adjacent tissues.5 It's the most common form of infectious uveitis. It has an annual incidence of 20.3 per 100,000 people.6
Anterior uveitis may result from eye trauma or underlying medical conditions such as rheumatoid arthritis, syphilis, tuberculosis (TB), sarcoid, or viral herpes. However, many cases of anterior uveitis have no identifiable cause (idiopathic).
- Red eyes
- Sore and inflamed eyes
- Blurred vision
- Light sensitivity (photophobia)
Treatment for anterior uveitis may include prescription eye drops and anti-inflammatory drugs. Dilating eye drops may cause some blurriness or increase light sensitivity. However, your eyes will feel more comfortable. This treatment lasts several weeks, and discontinuation is highly discouraged to avoid reoccurrence.
Oral steroids or injections may also come in handy if prescription eye drops fail.
4. High Blood Pressure Medications
According to The Centers for Disease Control and Prevention (CDC), hypertension affects nearly half of the U.S. population, with men being at a higher risk.7 The leading causes are poor diet, smoking, old age, alcohol use, stress, and genetics. In 2019 alone, hypertension resulted in more than 500,000 deaths.
Some medications such as clonidine and tetrahydrozoline, cause pupil constriction.
- Blurry or double vision
- Nausea and vomiting
- Elevated heart rate
- Shortness of breath
If your high blood pressure medication is causing your pupils to constrict to a pinpoint size, talk to your doctor about alternatives.
5. Horner syndrome
Horner syndrome (Bernard-Horner syndrome or oculosympathetic palsy) is a rare condition that may result from a tumor, stroke, spinal cord lesions, or brainstem damage.8 This condition affects the sympathetic nerve, which mediates pupil dilation.
According to research, Horner syndrome occurs in approximately 1 in 6,000 people and affects any age and ethnicity.9
- A significant difference in pupil size (anisocoria)
- Drooping upper eyelid (ptosis)
- Slight elevation of the lower eyelid (upside-down ptosis)
- Little or delayed dilation of the affected pupil in low illumination
- Sunken eye
- Little or no sweating on the affected side of the face (anhidrosis)
- Lighter iris color in children (one year or younger)
Currently, there's no specific treatment for Horner syndrome. In many cases, the condition will disappear after treating the underlying issue.
6. Head Trauma
Head trauma can cause serious complications even if you don't notice it immediately. Studies investigating the relationship between traumatic head injury and pinpointed pupils indicate a possible effect on the pupil's reaction time.10
If you notice pinpointed pupils after a road accident, this could signal a more serious internal issue.
- Loss of consciousness or coma
- Persistent or worsening headache
- Vomiting or nausea
- Blurred vision
- Convulsions or seizures
- Clear fluids draining from the nose or ears
- Weak or numb fingers and toes
- Loss of coordination
- Cognitive or mental symptoms
- Confusion and memory problems
- Slurred speech
- Change in eating or nursing habits (children)
You can relieve headaches due to head injuries with over-the-counter painkillers. Antinausea drugs will also help in case of any feeling of nausea or vomiting.
In the case of seizures, your doctor prescribes anti-seizure medications such as carbamazepine, clobazam, levetiracetam, clonazepam, etc. These medications work by stabilizing the brain's electrical activity.11
Less Common Causes of Pinpoint Pupils
- Certain medications such as Lomotil for diarrhea and phenothiazines for schizophrenia
- Neurosyphilis (syphilis of the brain)
- Deep sleep
- Iridocyclitis (inflammation of the iris and ciliary body)
- Aphakia (absence of the natural eye lens)
When to See a Doctor for Small Pupils
If you notice your pupils are abnormally small for no reason, reach out to your eye doctor. They'll conduct a diagnosis and prescribe proper treatment.
Lack of treatment may expose you to the following risks:
- Eye damage in the case of anterior uveitis
- Vision loss
- Coma in the case of opioid overdose
- Severe pain in case of eye trauma
- Worsening headache
- Stroke due to brain stem damage
In case of an overdose, contact Poison Control at 800-222-1222 or 911 for immediate assistance.
To diagnose pinpoint pupils, your doctor will conduct a comprehensive eye exam. Diagnostic testing may include:
- Magnetic resonance imaging (MRI)
- Computerized tomography (CT)
- Toxicology screening
- Blood tests
- Urine tests
Using these, your doctor will observe your pupils' appearance and behavior in light.
They may also administer dilating eye drops to rule out any eye diseases. If you're diagnosed with tiny pupils, your doctor will investigate the cause and commence treatment.
There’s no specific treatment for pinpoint pupils. This is because it’s not a disease but a symptom of several conditions. To determine treatment for your pinpointed pupils, your doctor must identify the underlying issue.
Seeking treatment early and following your doctor's recommendations is the best way to prevent life-threatening complications. If you use opioids, tell your doctor about it whenever you go for treatment.
Recovery from brain system damage may vary from person to person. However, how quickly you seek treatment can make a difference.
With anterior uveitis, permanent eye damage may occur if left untreated. The condition can also recur if it stems from an underlying problem. However, most people respond well to treatment.12
Finally, poisons from insecticides can be deadly if not treated properly. If you or your loved one is exposed to these poisons, seek immediate medical attention.
Pinpoint pupils are abnormally small pupils that don't respond to light. This condition is known as miosis or myosis. Pinpoint pupils can affect people of all ages and ethnicities.
Several factors contribute to pupil constriction: eye disease, substance abuse, prescription drugs, exposure to toxins, head trauma, and hypertension drugs.
If you suspect pinpoint pupils, your doctor will conduct an extensive eye exam to determine the cause and recommend treatment.
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