The part of your eye that controls the amount of light entering it is the pupil. Under normal circumstances, when compared to the iris, the pupil in your eye is usually round and medium in size. The amount of light entering your eye is controlled by the dilating or constricting of the pupil. When the light enters your eye through the pupil, the three photoreceptors i.e. the rod, ganglion and cone cells convert the light into electrical impulses, enabling you to see.
When the light is very bright, the pupils constrict or get smaller to restrict the amount of light entering and in the dark the pupils enlarge or dilate, which allows more amount of light to enter, improving your night vision.
This is the reason that when you enter a dark room, your pupils dilate and your eyes take some time to adjust to the surroundings and this is the same reason why your eyes are quite sensitive to light when, on a sunny day, your pupils get constricted.
The constriction and dilation of pupils are due to involuntary reflexes. You must have noticed that when you are ill or have had an injury, the doctor shines a light into your eyes. This is to determine if your pupils are reacting normally to the light or not.
The size of the pupil changes not only as a reaction to light, but the change can occur due to other stimuli too. For example, when you’re excited or on high alert, your pupils dilate, while other situations make them constrict. Normally, in adults, pupils measure 2-4 mm in bright light and 4-8 mm in darkness.
However, when the pupils constrict abnormally, then the condition is known as pinpoint pupils or miosis. Pinpoint pupils or abnormal miosis is when the pupils become abnormally constricted to less than 2mm when the light is normal.
The word “miosis” is from the ancient Greek language and stands for “to close the eyes”. There are several factors that cause our pupils to dilate abnormally, but there are very few factors that cause the pupils to constrict abnormally.
Pinpoint pupils can be caused due to many factors such as:
- Use of opioid drugs, benzodiazepine or miotic drugs
- Hemorrhage in the brain stem
- Horner’s Syndrome
- Exposure to chemicals like organophosphates or nerve agents
- Infections or neurosyphilis
Factors Causing Pinpoint Pupils
Drug Usage
Opioid Drug Usage
Opioid drug use is a common reason for pinpoint pupils. Opioid drugs are psychoactive substances that travel across the blood barrier via the central nervous system and affect your mental processes. Some of the popular opioids derived from the poppy plant are morphine, codeine, fentanyl, methadone, oxycodone, hydrocodone and heroin.
Opioid drugs are usually used for medical purposes to control pain. However, these drugs are easily misused, as these drugs can alter the states of perception and consciousness. Pinpoint or constricted pupils are a sign of drug overdose and can alert you to opioid drug usage.
Also, with regular abuse of opioids, people develop tolerance to the drug and exhibit pinpoint pupils although they are not overdosing.
Benzodiazepine Usage
Benzodiazepine, popularly known by its street name benzos, is also a psychoactive drug. These drugs are usually prescribed for problems such as anxiety, insomnia, panic disorders and seizures. Benzos are not safe for consumption if you’re pregnant. Just like opioid drugs, benzos also affect the nervous system in a similar manner and the usage and overdose of these drugs also cause pinpoint pupils.
Miotic Drugs Usage
Any drugs that cause the abnormal constriction of pupils are classified as miotic drugs. Both opioid drugs, as well as, benzodiazepines come under the category of miotic drugs.
However, some miotic drugs do not fall under these categories. For instance, carbachol is a miotic drug that is prescribed by ophthalmologists for certain conditions of the eye such as glaucoma. This is usually available in the form of eye drops and its use can cause pinpoint pupils. Other eye drops like pilocarpine, epinephrine, echothiophate and demecarium can also cause pinpoint pupils.
Exposure to Chemicals or Nerve Agents
Pinpoint pupils may be caused due to exposure to certain kinds of chemicals such as organophosphates. These chemicals are usually used in the production of pesticides.
If you are exposed to organophosphates, the parasympathetic system is overstimulated. If you get too much of exposure to these chemicals, you can suffer from an increase in body fluids, muscle cramps and pinpoint pupils. When such symptoms are seen, you must see a doctor immediately to rule out pesticide poisoning.
Exposure to nerve agents that are usually used in chemical warfare such as VX, sarin, tabun and soman also cause pinpoint pupils.
Problems in the Brain
Pinpoint pupils can be caused due to bleeding occurring from a blood vessel in the brain or intracerebral hemorrhage or due to pontine infarctions. Pontine infarction occurs when the tissue in the pons region of the brain dies due to deficiency of blood supply. Both these conditions can occur due to stroke, illness or traumatic brain injury.
If the frontal portion of the brainstem is injured, then the pupils of both eyes will be constricted. If any other part of the brain is injured, then the pupils of both eyes may be of different sizes, one may be constricted, while the other may be dilated.
If you notice pinpoint pupils and the person has a previous history of brain trauma or stroke, then you must have the condition checked by the doctor immediately.
Infections
Sometimes, pinpoint pupils are caused by viral or bacterial infections. For example, anterior uveitis is an infection that affects the iris and the middle portion of the eye. This may be caused due to some foreign particle in the eye or due to trauma to the eye.
Depending on the kind of infection and its severity, inflammatory adhesions may form between the iris and the lens. These adhesions can cause the tissues in your eye to stick together that makes it very difficult for the pupils to expand and contract normally, thus causing pinpoint pupils.
Neurosyphilis
Pinpoint pupils are not only caused due to infection in the eye. Pinpoint pupils may be an indication of some other infection like neurosyphilis. For example, if your spinal cord or brain is affected, this changes how your pupils react when exposed to light. Neurosyphilis is caused by the same bacteria that cause syphilis.
Horner’s Syndrome
Horner’s syndrome, also known as Horner-Bernard syndrome or oculosympathetic palsy, is a physical disorder that affects the nerve pathway between one side of the face and the brain. Horner’s syndrome may be caused by itself without any determined cause or may be due to a tumor, stroke or spinal cord injury.
The classic symptom of this condition is pinpoint pupils along with drooping eyelids. Also, there is reduced perspiration on the affected part of the face. Babies that are born with Horner’s syndrome have one iris that is lighter in color than the other.
Other Causes of Pinpoint Pupils
A very common reason for pinpoint pupils is hypertension or high blood pressure that is not controlled. Pinpoint pupils may be caused due to other conditions such as mumps, rubella and rheumatoid arthritis.
Other less common causes for pinpoint pupils are: medications like Lomotil prescribed for diarrhea, clonidine for high blood pressure, phenothiazines for psychiatric conditions such as schizophrenia and illicit drugs like mushrooms. Sometimes, even deep sleep can cause you to have pinpoint pupils on waking up.
Symptoms of Pinpoint Pupils
Pinpoint pupils are not a disease, but a symptom that may give you a clue about what is actually causing the problem.
Opioid Drug Usage
If a person is taking opioids, apart from pinpoint pupils, other symptoms may include nausea and vomiting, sleepiness, lack of alertness, confusion, difficulty in breathing, delirium, etc.
The symptoms depend on the amount of drugs taken and the duration of drug intake. In the long run, use of opioids can cause reduced lung function and addiction to opioid drugs can include signs such as:
- Severe cravings for the drug.
- Requiring bigger doses of the drug to get the desired effect.
- Financial problems and trouble at home and at the workplace caused by drug usage.
Intracerebral Hemorrhage
If the pinpoint pupils are due to hemorrhage in the brain, you may experience nausea, vomiting and headache and you may also lose consciousness.
Horner’s Syndrome
In the case that the pinpoint pupils are because of Horner’s syndrome, your eyelid may begin to droop and the affected side of the face may have decreased sweating.
Infections
If you are suffering from anterior uveitis, other symptoms such as inflammation, redness, light sensitivity and blurred vision may occur, apart from pinpoint pupils.
Chemical Exposure
Poisoning caused by pesticides and insecticides can cause other symptoms such as tearing, salivation, vomiting, excessive urination and defecation, and exposure to nerve agents may cause problems like vomiting, tearing, seizures and even coma.
Treatment for Pinpoint Pupils
Since pinpoint pupils is not really a disease and is a symptom of a disease, there is no particular treatment for the condition. However, pinpoint pupils can lead you to find the correct diagnosis and guide you in the treatment of the particular problem.
In the case of an opioid drug overdose, emergency medical staff can make use of the drug, naloxone that can help to reverse the effects of the opioid overdose, which can even be fatal.
The condition of intracerebral hemorrhage may sometimes even need surgical intervention to stop the bleeding. Also, the treatment must include steps to keep the blood pressure of the patient under control.
There is no medical treatment available for Horner’s syndrome. However, if the cause of the disease is established and treated, it can get better.
Anterior uveitis and other infections can be treated by the use of corticosteroids and topical medications such as ointments and eye drops.
Poisoning caused due to insecticide usage can be treated by using the drug, pralidoxime or 2-PAM.
When You Should Seek Medical Help
If you notice that your pupils are abnormally constricted into pinpoints and you are not really able to understand why, then it is a good idea to see your general physician or your ophthalmologist to get a proper diagnosis and treatment.
Procedure of Diagnosis
Your doctor will arrive at the diagnosis of your problem after evaluating the various symptoms and signs and may also ask for a few diagnostic tests to be conducted.
If you decide on seeing your ophthalmologist when you notice pinpoint pupils that are not normal, then your doctor will conduct a complete examination of your eye. The doctor may dilate your eyes, so that the inside of the eye can be visually examined.
In the case that you decide to see your general physician, then the doctor may conduct some diagnostic tests to identify your problem. You may be asked to get an MRI (magnetic resonance imaging) scan, CT Scan (computerized tomography), X-rays, blood and urine tests and a toxicology screening.
Course of Treatment
Opioid Overdose
Opioid overdose can be life-threatening and can even cause death. Any of the following symptoms indicate opioid overdosing and requires immediate medical attention:
- Pale and clammy face
- Blue or purple colored fingernails
- Limp body
- Gurgling or vomiting
- Heartbeat slowing down
- Difficulty in breathing or labored breathing
- Loss of consciousness
In the case of an opioid overdose, your recovery will depend on factors such as:
- If the opioid drugs were mixed with other substances and what those substances were.
- Whether you continued breathing or not. If you stopped breathing, then what was the duration that you did not have any oxygen.
- If you suffered an injury that may have caused permanent respiratory or neurological damage.
- If you suffer from any other medical conditions.
- If you continue to use opioid drugs.
In the case that you have had any issue with substance or opioid abuse, ensure that you tell your doctor when treatment is being administered. A point to note is that opioid or substance abuse is a very serious problem and requires long-term attention.
Intracerebral Hemorrhage
If you have suffered from intracerebral hemorrhage, your recovery really depends on how quickly you are treated and how well your blood pressure is controlled.
Anterior Uveitis
Anterior uveitis may result in permanent damage to the eyes if not treated immediately. Sometimes, anterior uveitis can be a recurring problem due to some other illness and must be attended to immediately. Nevertheless, anterior uveitis is a condition that is quite easy to treat.
Insecticide Poisoning
Poisoning due to insecticide or pesticide use can be very dangerous if not treated properly. It is critical to get immediate attention if you think that you have been exposed to pesticides or insecticides that may have caused poisoning.
Constricted pupils are a phenomenon that you may encounter quite commonly. However, abnormally constricted pupils or pinpoint pupils are a cause of concern. While many times, this condition may not be anything serious, very often they are the symptoms of a more serious underlying complication that must be attended to immediately.
