Rapid Diagnosis: Pinpoint Pupils
Abnormally constricted or “pinpoint” pupils are a great finding for our rapid diagnosis series. There are many things that can cause the pupil to abnormally dilate. Very few things will make the pupil abnormally constrict. Constricted pupils are a doorway to a very short list of ailments and with a bit of background you should be able to hang your hat on one fairly quick.
How do we assess for “pinpoint” pupils?
Recall that the pupil should be mid-range and reactive under normal lighting conditions. When subjected to bright light, the pupil will constricted to reduce the volume of light entering the iris. In darkness the pupil will dilate to allow as much ambient light in as possible. Pupils smaller than 2mm in diameter under normal lighting conditions can be considered “pinpoint”. Any pupil that responds to changes in lighting conditions with 1mm of movement or less can be considered minimally reactive or nonreactive.
To assess for pinpoint pupils we need to subject the pupil to darkness by asking the patient to close their eyes or covering the patients eye. When we return the light source to the pupil we expect the pupil to be larger and rapidly return to its original size. If the pupils remain <2mm in diameter through the changing light conditions we have a “pinpoint pupils” finding. The fancy medical term for this phenomenon is abnormal miosis.
If the patient has bilateral pinpoint pupils consider the following possible etiologies:
1.) Opiate use / abuse / overdose
Opiate class drugssuch as Heroin, Fentanyl, Codeine, Methadone and Morphine stimulate the parasympathetic side of the autonomic nervous system and cause pupil constriction. While it varies depending on your response area, most of the constricted pupils that you encounter in the field will be opiate induced.
Look for possible sources of drug use or abuse from prescription meds to illicit drugs. Evaluate the patient for track marks across the veins and the scene for paraphernalia like spoons, tin foil, matches, syringes and makeshift tourniquets. Don’t rule out opiates in pediatrics. Miosis in combination with depressed respirations are the hallmark signs of opiate overdose.
2.) Pontine Hemorrhage
The pons is a knob-like structure located at the front of the brain stem. Intracranial hemorrhage in the area of the pons will typically cause bilateral pupil constriction. Intracranial hemorrhage can have both traumatic and atraumatic origins.
Consider pontine hemorrhage in the presence of high mechanism head trauma and patients with a history of vascular disease, strokes and abnormal bleeding. If you find miosis with altered mental status that does not respond to Narcan administration, consider the possibility of a pontine hemorrhage.
3.) Organophosphate / Chemical / Nerve Agent Exposure
There are a few classes of chemicals that cause parasympathetic over-stimulation and, therefore, pinpoint pupils. Organophosphate chemicalsare the most common. Virtually any phosphorous-containing organic compounds are considered organophosphates.
These compounds are effective pesticides used in agriculture. They are widely used because they break down easily in the environment unlike their cousin DDT. Malathion and parathion are examples of organophosphate pesticides. These chemicals kill insects by disrupting their nervous system function. Unfortunately they kill humans in the same manner.
They can be absorbed through the skin, inhaled and ingested. Once absorbed they shut down acetylcholinesterase production and put the parasympathetic system into overdrive. This will create the classic SLUDGE presentation, characterized by excessive salivation, lacrimation (tears), urination, defecation and emesis. And two other telltale signs (If you needed more) … muscle cramps and pinpoint pupils.
Many of the never agents used in terrorist attacks are organophosphate in nature including Sarin and VX gas. If your patient is involved in farming or agriculture, drank an unknown chemical or was a victim of a chemical attack, check for pinpoint pupils and consider organophosphate poisoning.
So there you have it. OK, sure, we’ve left out a few possibilities here. Hopefully you’ll forgive me for passing over Horner’s Syndrome, Neurosyphilis and a few other obscure brain abnormalities that will cause abnormal pupil constriction. No diagnosis is a certainty, but when you find those pinpoint pupils, start with the big three. Now go look at some pupils.
Related Articles:
Five Assessment Findings That Should Concern You
Understanding Combative Head Injuries
Five Trauma Scene Mistakes You Should Avoid
Tags: Assessment, autonomic, constricted pupils, diagnosis, EMS, EMT, miosis, parasympathetic, pinpoint pupils, pupil, pupil assessment, pupil size
Steve, thanks again for posting this stuff on the web so students and experienced EMTs alike can all learn from this site. I really found this post helpful especially for Medical Assesments where origin may not be so easy to find as being ejected from a vehicle. Thanks again Steve and it was fun to watch ya get tied up in class tonight.
Hey, your welcome Alan. And I’m glad I could be an adequet, if unplanned, substitute for a combative patient for the class.
thanx
great info, but please spe;ll correctrly:
neuorsyphilis not neurosyphilus
and pontine not pontiene
Thanks Dr. P. I have corrected both errors. I appreciate your editorial heads-up.
@nony You’re welcome.
I was able to get whole information about the topic from here which I could not find anywhere…
I am a TLE pt w/long post-ictal times where I can hear, feel, but cannot talk, move, respond. I have, right now, a lump and bruise from repeated sternal rubs that I felt but was unable to respond to. Vitamin A – ammonia under or UP the nose does not work and with COPD, it is very disturbing. My eyes are the first to “come back”, speach comes back as “moaning”, legs/arms can take 12 or more hrs to come back. Full, normal speach, can take up to 24 hrs. THIS IS REAL – documented. Laughing, talking psych, etc. may anger me, but I cannot tell you that – because I cannot talk. I take MANY epileptic meds and no psych meds and live a facility because of the epilepsy, COPD, CH, PVD, etc. 2x I had “grand-mal” and “coma” from low potassium and once from low magnesium. My seizures began when I was 18 mos old – same as now – staring, stiffening, going limp and unresponsive, then poof – back to reality with amnesia for the event. PLEASE TRAIN YOUR EMT’S FOR POST-ICTAL/ICTYL STAGES and the various TYPES of epilepsy. My vitals are usually normal – just unresponsive due to epilepsy – NOT psych. Thank you. God bless you.
thanks mate, you learn something new everyday. i never realized opiate could cause pinpoint pupils- rather, i always thought they dilated them like most other drugs. again, thanks
As I found out last night, theres one more thing that can cause pinpoint pupils: SKUNK SPRAY. One of my dogs got a load into her eye and that eye constricted to pinpoint within a couple minutes. I did the usual skunk wash (Dawn dish detergent, baking soda and hydrogen peroxide) around her eye, then tried irrigating her eye with water, but that was difficult. As it was evening, she bedded down for the night and about an hour after the incident her pupil started growing slightly. By morning it was normal and her eye looked fine. She had no irritation or watering in the eye either.
Now – what skunk spray contains to do that is beyond me, however it may have evolved as part of the defense mechanism as when pupils constrict – you cannot see and the skunk escapes the predator.
Really.thanks on greate information
Just found your site today while resting after a gastro- bug bite. Am in process of renewing my teaching certification for EMT after several years of just practicing medicine as a PA. I am very impressed with what I have seen of your content, and plan to make your site required reading for future students. The Pinpoint Pupil article is a classic in that it puts all the emphasis on constriction without mentioning dilation to any degree. As a result the confusion that often occurs to a student is avoided, since the issue of dilation can then be implanted in a separate class or article. Thank you for your perspective on 3 minutes, 3hrs, 3 weeks. That is a classic also, and one that must be impressed from the very first class to all potential EMS students.
Keep them coming
Gale
i have big time pinpoint pupils and they rarely dialate. it is always small and never gets big, i wonder why
Excellent info. It is hard to find such info in ophthalmology texts
Hey, I wanted to delve into my 1mm diameter constricted pupils from last night to 12 pm this afternoon. It was caused a stimulant, though. Concerta (methylphenidate) to be exact. Im not a crazy druggie or anything, but I do realize that I took 216 mg of concerta xr all within 20 minutes, and it caused slight paranioa, intense heart beat, and unbalanced depth perception (because if i looked at my laptop, it seemed like it kept shifting). Just wanted to help out.
P.S. I was planning on taking 150 mg which is double my dose, and i wanted to seewhat would happen. I failed at keeping track though XD. NOT DOING THAT AGAIN!