What drugs cause constricted pupils?
Detecting Drug Use Through Pupil Constriction
While excessive pupil dilation can indicate potential substance use, the opposite phenomenon - pupillary constriction or miosis - can also signal drug impairment. Miosis occurs when the iris sphincter muscle contracts and the pupil sizes become abnormally small or "pinpoint." This limits the amount of light entering the eye and can be a key indicator for abuse of certain substances.
Gaize measures pupil size to a precision of 0.01 millimeters, 90 times per second (at 90 hz). This allows the product to capture an enormous amount of data that can be analyzed by machine learning models to detect potential drug use and abuse. Measurement of constricted or pinpoint pupils and their reaction to varying levels of light is critical in the impairment detection process.
Drugs That Cause Constricted or “Pinpoint” Pupils
Certain classes of drugs, particularly opioids (both natural and synthetic) and opioid derivatives, are known to cause miosis by disrupting the normal functioning of the autonomic nervous system that regulates pupil diameter.
Opioids: Drugs like heroin, oxycodone, hydrocodone, and fentanyl activate mu-opioid receptors in the brain. This stimulates the parasympathetic nervous system, causing the pupils to constrict along with other physiological effects like slowed breathing and heart rate.
Other Drugs: Other substances that may induce miosis (constricted pupils) include:
Clonidine (used to treat high blood pressure)
Tizanidine (a muscle relaxant)
Phenothiazine antipsychotics like chlorpromazine
Pinpoint pupils can occur at typical or higher therapeutic doses of these medications. However, with sustained opioid use, tolerance can develop, potentially making pinpoint pupils a less reliable sign of use.
Assessing for Pupil Constriction to Determine Substance Use and Abuse
Like pupil dilation, pinpoint pupils alone cannot conclusively prove substance use or intoxication. Pupillary constriction can also result from other factors such as:
Direct trauma to the eye
Diseases affecting the brain or muscles controlling the pupils
Oxygen deprivation
Environmental influences like bright light exposure
To evaluate for potential opioid or other drug impairment, law enforcement and medical personnel are trained to look for miosis along with other corroborating indicators through standardized assessment tools:
Drug Recognition Expert (DRE) Evaluations: The 12-step DRE protocol includes examining pupil sizes along with vital signs and physiological indicators associated with various drug categories.
Pupillometry Scales: Visual measurement charts depict constricted pupil sizes that may suggest opioid use when present with other clinical signs.
While pupil constriction raises suspicion of opioid influence when other suggesting factors exist, confirming impairment typically requires additional screening through questioning, cognitive testing, and potentially chemical tests. Gaize evaluates pupil size as a key part of the impairment detection process.
By understanding how certain drugs like opioids can cause pupillary constriction or "pinpoint pupils," Gaize can leverage this knowledge alongside other assessment tools to help identify potential substance impairment. However, pupil constriction should not be interpreted in isolation, but rather as part of a test like Gaize, or through medical evaluation.
References:
An evaluation of pupil size standards used by police officers for detecting drug impairment Jack E. Richman, O.D.,a Kathleen Golden McAndrew, M.S.N., ARNP,b Donald Decker,c and Stephen C. Mullaney, B.S., M.S.d
https://www.theiacp.org/sites/default/files/all/i-j/JAOA%20Pupil%20Size%20paper%20Richman.pdf
Packiasabapathy S, Rangasamy V, Sadhasivam S. Pupillometry in perioperative medicine: a narrative review. Can J Anaesth. 2021 Apr;68(4):566-578. doi: 10.1007/s12630-020-01905-z. Epub 2021 Jan 11. PMID: 33432497; PMCID: PMC7935761.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7935761/
Rollins MD, Feiner JR, Lee JM, Shah S, Larson M. Pupillary effects of high-dose opioid quantified with infrared pupillometry. Anesthesiology. 2014 Nov;121(5):1037-44. doi: 10.1097/ALN.0000000000000384. PMID: 25068603.
https://pubmed.ncbi.nlm.nih.gov/25068603/
