Miosis is an excessive constriction of the black spot in the center of your eyes. The term is from the ancient Greek μύειν, mūein, “to close the eyes.”
The black circle in the center of your eye is your pupil. It changes size thousands of times a day. Under normal conditions, the pupils change in size to let in the correct amount of light.
In the dark, they open wider or dilate to let in more light; in bright light, they shrink or shrink to prevent too much light from entering.
However, some medical conditions and the use of certain medications can cause the pupils to shrink to a precise size.
When your pupil contracts, it is called miosis . If your pupils remain small even in low light, it may be a sign that things in your eyes are not working the way they should. This is called abnormal miosis, and it can occur in one or both eyes.
The opposite condition, mydriasis , is the dilation of the pupil. Anisocoria is the condition of one pupil that is more dilated than the other.
Study of the primary miotic pupils of Adie
Two young adults, ages 24 and 31, had a long history of small, unreactive pupils. There was no history of large pupils, and a review of old photographs confirmed 10 and 5 years, respectively, of miosis.
Both were found to have bilateral tonic pupils that were supersensitive to dilute pilocarpine.
Although it is possible that they had an unusually early onset of bilateral Adie syndrome with dilated pupils that was not noticed, it is suggested that some patients may have primary miotic pupils of Adie without going through a mydriatic phase.
Miosis is a persistent constriction of the pupil due to excessive constriction of the iris sphincter muscle or paralysis of the pupil dilator muscle .
Among the many causes, consider:
Irritation of the sympathetic nerve that innervates the longitudinal fibers of the iris, a lesion of the trigeminal nerve, in relation to the sympathetic system of the iris or a problem of the central nervous system: medullary or cortical.
Paralytic miosis, a condition of the sympathetic nervous system and associated with Horner’s syndrome, presents with the drooping of the eyelid and the sinking of the eyeball into the orbital cavity.
The length of the course of the sympathetic fibers from the thalamus to the long ciliary nerves explains the multiplicity of possible causes of this syndrome.
Senile miosis (a reduction in the size of a person’s pupil in old age).
It is normal for a newborn’s pupils to remain small for about 2 weeks so that his eyes have extra protection from bright light. Your pupils tend to get smaller as you get older, too.
The muscles that work your pupils can become weak and have a hard time opening them. This can make it harder for you to see at night.
- Lumpy hemorrhage (intracranial hemorrhage).
- Hereditary disorders.
- Cluster headaches with ptosis.
- Fatal family insomnia.
This rare condition affects the way your brain “talks” to one side of your face, including one of your eyes. It can make one of your pupils smaller than the other.
You can inherit it from your parents, or it can happen after a neck injury or neck surgery.
You can also get it if your chest, neck, or brain is not formed properly. Sometimes children get it if they have a rare type of cancer called neuroblastoma or a tumor in another part of their body.
Horner syndrome may not cause other symptoms, or you could have problems such as:
- Droopy upper eyelid (ptosis).
- Lower eyelid raised.
- Lighter eye color in the eye with miosis (heterochromia).
- Less sweat on the side of your face with the miotic eye.
Swelling inside the eye can make it difficult for the pupils to grow. Sometimes this happens if you have injured your eye. It can also be due to a condition called uveitis, which is swelling in the iris, the part that gives the eye its color, and the tissues around it.
While many people with anterior uveitis are otherwise healthy, it can be associated with:
- Rheumatic disease
- Skin diseases.
- Gastrointestinal disease.
- Lung disease.
- Infectious disease
It occurs mainly in young or middle-aged people and can appear in one or both eyes.
It may be due to trauma to the eye or something foreign to the eye. Other causes include rheumatoid arthritis , mumps, and rubella. Often times, the cause cannot be determined.
Bleeding from a blood vessel in the brain (intracerebral hemorrhage)
Uncontrolled high blood pressure (hypertension) is the most common reason for this. A 2014 study evaluated the importance of how the pupils react to light when there are potential injuries to the central nervous system.
For people who have suffered head injuries in car accidents or other accidents, pinpoint pupils can be a sign of serious internal problems.
Head injuries can cause serious and even life-threatening complications, even if the effects are not immediately apparent. Anyone who has suffered a head injury should seek immediate medical attention.
Several conditions and drugs can cause pinpoint pupils, including:
Prescription or narcotic opioids
Some medications have opioids or narcotics in them. Opioids, including morphine, are medications commonly used to relieve pain. Opioids can affect a person psychologically and are highly addictive.
People often take prescription opioids in pill form to treat severe postsurgical pain, such as dental surgery, or for long-term pain, as with some cancers.
Prescription opioids (the notable exception being pethidine), which can cause pinpoint pupils include:
Methadone is often used to help a person who is dependent on opiates to recover from their addiction slowly and with manageable withdrawal symptoms.
Pointed pupils are one of the signs of heroin use. Heroin is a highly addictive recreational opioid.
It slows the body down and is a powerful pain reliever, causing the person to relax and numb.
People who use heroin are at risk for blood infections from sharing needles. Heroin injection can also damage veins and arteries and can cause gangrene.
Heroin can also cause respiratory failure (when a person stops breathing) or death from inhaling vomit, as it limits the person’s ability to cough properly.
Products that contain nicotine, such as cigarettes, chewing tobacco, or gum. Imidazolines such as clonidine, naphazoline, oxymetazoline, and tetrahydrozoline. Antipsychotics, including risperidone, haloperidol, chlorpromazine, olanzapine, quetiapine, and others.
Cholinergic agents such as acetylcholine. Acetylcholinesterase inhibitors. Ondansetron (an antiemetic) known by its brand name Zofran
Some cancer chemotherapy drugs, including camptothecin derivatives. Mirtazapine, a noradrenergic serotonergic antidepressant.
Some MAO (monoamine oxidase) inhibitors. Pilocarpine eye drops and all other parasympathomimetics. In some rare cases, when exposed to mustard gas. Organophosphates.
Certain prescription drops, such as pilocarpine, carbachol, echothiophate, demecarium, and epinephrine, can also cause pinpoint pupils.
Being born without the muscle that controls your pupils or with the muscles of the pupil that do not form correctly is called myiosis or congenital microcoria. You get it when one or both of your parents pass on a problem gene to you.
It can happen in one eye or in both eyes. If you do, you may also be nearsighted and have trouble seeing distant things. Or you may have glaucoma, which means there is too much pressure inside your eyeball.
Side effect of a medication
Certain types of anxiety, muscle spasms, and seizures, such as diazepam (Valium) or antihistamines such as diphenhydramine (Benadryl), can cause your pupils to shrink.
Some prescription drugs for high blood pressure (hypertension) can also cause pinpoint pupils
Exposure to chemical neurotoxic agents
Like sarin, soman, tabun and VX, they are not natural substances. They are made for chemical warfare. Insecticides can also cause pinpoint pupils.
Research suggests that accidental exposure to pesticides (organophosphates) can cause pinpoint pupils in some cases. The person may also show signs of:
- Excessive saliva
- Nausea and vomiting
- Trouble breathing
- Muscular weakness.
- Rapid pulse.
In 2016, the World Health Organization (WHO) estimated that 3 million people are poisoned by pesticides each year.
Symptoms associated with miotic pupils
Point pupils are a symptom, not a disease. Accompanying symptoms can offer a clue as to what is causing the problem.
If you take opioids, you may also experience:
- Nausea and vomiting
- Confusion or lack of vigilance.
- Labored breathing
Symptoms will depend on how much medicine you take and how often you take it.
Physiology of the photomotor reflex
Light entering the eye affects three different photoreceptors in the retina, the familiar rods and cones used in imaging, and the more recently discovered photosensitive ganglion cells.
Ganglion cells provide information on ambient light levels and react slowly compared to rods and cones.
Signals from photosensitive ganglion cells have multiple functions, including acute suppression of the hormone melatonin, entrainment of the body’s circadian rhythms, and regulation of pupil size.
Retinal photoceptors convert light stimuli into electrical impulses. The nerves involved in the change in pupil size connect to the pretectal nucleus of the superior midbrain, bypassing the lateral geniculate nucleus and the primary visual cortex.
From the pretectal nucleus, neurons send axons to neurons in the Edinger-Westphal nucleus whose visceromotor axons extend along the left and right oculomotor nerves.
Visceromotor nerve axons (constituting a portion of cranial nerve III, together with the somatomotor portion derived from the Edinger-Westphal nucleus) synapses in ciliary ganglion neurons, whose parasympathetic axons innervate the iris sphincter muscle, producing miosis.
This occurs because the sympathetic activity of the ciliary ganglion is lost, so the parasympathetics are not inhibited.
When to seek help
Pinpoint pupils are not a disease in and of themselves, but they may indicate an underlying medical problem.
Anyone who experiences pinpoint pupils for no apparent cause should see a doctor as soon as possible.
Many of the causes of pinpoint pupils are serious medical conditions, such as opiate dependence or pesticide poisoning. Early intervention can help prevent life-threatening complications.
Even anterior uveitis can cause permanent eye damage and blindness if left untreated.
However, the outlook for conditions that cause precise pupils improves when people seek quick treatment and follow a doctor’s advice for a full recovery.
If you have pinpoint pupils for unknown reasons, see your ophthalmologist or general practitioner. It is the only way you will get a proper diagnosis.
To find out if you have abnormal miosis, your doctor will watch you closely in a dark room. She will ask you to look at a distant object. Then she will check:
- The size of your eye.
- The shape of your eye.
- If your pupils are equal in size.
- The position of your pupils.
- How your pupils react to bright light.
Normal pupils have 2 to 4 millimeters in bright light and 4 to 8 millimeters in the dark. Your doctor can measure your pupils in both eyes to see how well they shrink and grow.
What to Expect During Diagnosis
How your doctor approaches the diagnosis will, of course, depend on the big picture. Accompanying signs and symptoms should be considered and guide diagnostic testing.
If you are visiting an eye doctor because your pupils do not appear normal, you will likely have a complete eye exam. This will include dilation of the pupil so the doctor can visually inspect the inside of your eye.
If you visit your doctor, other diagnostic tests may include:
- Magnetic resonance imaging (MRI).
- Computed tomography (CT).
- Blood test.
- Urine tests.
- Toxicology test.
An opioid overdose can be fatal. These symptoms, which may indicate an overdose, require emergency medical attention:
- The face is pale or clammy.
- Nails are purple or blue.
- The body is flaccid.
- Vomiting or gurgling
- Slowed heartbeat
- Slow breathing or shortness of breath
- Loss of consciousness.
Your doctor’s recommendations will depend on what is causing your abnormal miosis. This condition interferes with visual acuity, and it is necessary to enlarge the pupil.
The pupil can be artificially enlarged using photomidriasis or through a sphincterotomy procedure. Photomidriasis is a similar procedure to pupilloplasty, but takes place around the pupil.
A sphincterotomy is accomplished by radial Nd: YAG laser cuts of the sphincter muscle (energy 2-4 mJ).
Using a special lens that increases and focuses the thermal energy of the laser, sphincterotomy can also be performed by means of thermal laser burns using 1 W of power, a spot size of 50 μm, and an interaction time of 0.05 s.
In miotic pupils, the laser can be used to enlarge the pupillary area by contracting the collagen fibers of the iris and widening the pupil. Applications should first be 200 μm spots of 200-500 mW for 0.1-0.2 seconds.
It is important to start with very low energy levels and increase power until the desired effect is seen. Dark brown irises absorb much more energy than iridescent irides, so the level of treatment must be tailored to the individual patient.
Applications should be placed in a row peripheral to the pupillary edge and peripheral to the sphincter to avoid inadvertent exposure to the retina when transferring light.
Another series of lasers with a spot size of 500 μm should be placed only peripherally in the first row. Its effect, however, may not be permanent if miotics are resumed. Care must be taken to avoid burning or vaporizing tissue and to avoid injury to the retina.
If your pupils are small due to inflammation in your eye, you may give long-acting dilating drops (atropine or homatropin) that will make your pupils larger.
They look a lot like the drops your eye doctor uses to dilate your eyes during an exam, but they can last up to 2 weeks.
Prescription or narcotic opioids
Opioid overdoses can be fatal if left untreated, so anyone with a suspected overdose needs emergency medical attention.
A person who experiences an overdose will receive naloxone, which blocks the effects of opioids. A doctor may also refer them to a treatment and recovery program if they are dependent on drugs.
Medications for hypertension
If a drug is to blame, you may be able to find a different option that solves the problem.
Anyone who thinks their hypertension medication may be causing pinpoint pupils should speak to their doctor. Your doctor may prescribe a different form of medicine.
A person with heroin dependence should speak to their family doctor or a local drug treatment center.
A health professional will ask you about your drug use, your family and living situation, and any other contributing factors that the person wishes to disclose. The doctor may request a urine or saliva sample.
There are a range of treatment options available, depending on the individual’s needs. These include:
- Talk therapy, cognitive behavioral therapy (CBT), or other counseling.
- Support groups.
If Horner syndrome is causing it, you may need to do several tests to find out the best way to treat it. You may need surgery for problems in your arteries or brain.
Horner syndrome can be a sign of life-threatening neck or upper body complications, so seeking medical attention is essential.
Inflammation of the eye (anterior uveitis)
Treatments for the pointy pupil caused by anterior uveitis include:
- Using eye drops to open the pupil.
- Using steroid-containing eye drops to reduce inflammation.
A doctor or eye doctor (ophthalmologist) may refer a person for further testing if they suspect an underlying medical condition is the cause.
Exposure to pesticides
Anyone who thinks they or someone else has been poisoned by a pesticide, household cleaner, or other toxic product requires immediate medical attention.
If a person is unconscious or vomiting, it is important to roll them onto their side if possible and keep the head slightly downward. This position will ensure that any vomit can escape without the person suffocating.
Medical treatments for poisoning include:
- Activated carbon.
- Antidotes, if possible.
- Antiseizure medications.
- A respirator (ventilator).
The outlook depends on the cause and the treatment.
For an opioid overdose, how well you recover and how long it will take depends on:
- Whether or not you stopped breathing and how long you were without oxygen.
- If opioids are mixed with other substances and what are those substances.
- Whether or not you suffered an injury that causes permanent neurological or respiratory damage.
- If you have other medical conditions.
- If you continue to take opioids.
If you’ve ever had a problem with opioid or other substance abuse, let your doctors know when you need treatment, especially for pain. Addiction is a serious problem that requires long-term care.
Recovery from intracerebral hemorrhage differs from person to person. Much depends on how quickly you received treatment and how well you can control your blood pressure.
Without treatment, anterior uveitis can permanently damage your eyes. When due to an underlying disease, anterior uveitis can be a recurring problem. Most people respond well to treatment.
Insecticide poisoning can be fatal if not treated properly. If you believe that you or someone you know has been poisoned by insecticides, it is important to seek medical attention immediately at the nearest emergency room.