March 9, 2021

Looking at the Eye's Pupil Size for Effective Opioid Agonist Therapy

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New research shows that pupillometry using an automated camera could improve treatment for opioid withdrawal symptoms and outcomes.

THE BOTTOM LINE   |   The use of and withdrawal from opioids affects an individual’s pupil size. So, clinicians can use more precise pupil measurements to help improve both the medication-based management of opioid withdrawal symptoms and outcomes in these patients.

CONTEXT   |   Methadone and buprenorphine are the most common medications used for opioid agonist therapy (OAT), which treats withdrawal symptoms as well as reduces cravings to use opioids. For individuals seeking treatment for substance use disorder with OAT, certain factors play into how a provider determines a patient’s most effective dosage, which varies widely from person to person. The Clinical Opiate Withdrawal Scale (COWS) is a 48-point system that measures withdrawal severity by allotting points based on several factors, including pupil dilation. The higher the score indicates a more severe withdrawal classification. 

An individual’s pupil size is affected by many factors, but one is the use of and withdrawal from opioids. Calculating the resting pupil size during a COWS assessment is scored as “normal for room light,” “possibly larger than normal for room light,” and “moderately dilated,” and “so dilated that only a rim of iris is visible.” This subjective measurement can lead to inter-observer variability and does not take into account the difference in pupil sizes among individuals, which could result in sub-optimal initial dosing of OAT.

STUDY OBJECTIVE   |   To determine if using a handheld automated camera to measure pupil size and dilation — automated pupillometry — is more useful and objective than the current practice. 

THE DETAILS   |   This was a prospective cohort study that included 27 patients set to receive OAT to treat opioid withdrawal symptoms and cravings during an acute hospital stay. Precise automated pupillometry measurements were taken six times at regular intervals before and after OAT was administered. Pupil observations were also taken using current COWS methods both before and after OAT was given. Primary outcomes included pupil size in both dark and light settings, and secondary outcomes included latency of pupillary light response, constriction and dilation velocity (mm/s), and percent constriction.  

FINDINGS   |   Prior to the first OAT dose, the mean pupil size in dark and bright light settings was 4.33mm and 2.96mm, respectively. At 15 minutes after OAT, mean pupil size decreased significantly to 4.01mm in the dark and 2.71 in bright light. The larger the change in pupil size is associated with better control of opioid withdrawal symptoms.

Given the subjective nature of COWS, the pilot study informs future work to incorporate automated pupillometry’s objective measurements — with little training needed to use the camera — into OAT dosing assessments 

PULL QUOTE   |   “The technological capabilities of this camera have recently been made available in the form of free or inexpensive smartphone applications, which means that this more precise pupil measurement tool can help expand access to addiction treatment across the country. The next step in our research is to validate these applications as they would significantly decrease barriers to adoption of careful pupil size measurement in addiction treatment,” says Crandall Peeler, MD, an ophthalmologist at Boston Medical Center and the lead author of the paper.

Source: Peeler, CE, Gorgy, M, Sadlak, N, Sathe, S, Tamashunas, N, Fiorello, MG, Cabral, H, Paasche-Orlow, MK, Weinstein, ZM. (2020). “A Pilot Study of Automated Pupillometry in the Treatment of Opioid Use Disorder.” Journal of Addiction Medicine.

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About the Author

Jenny Eriksen Leary

Jenny is a former associate director of media relations at Boston Medical Center and has more than 15 years of experience in healthcare communications and public relations.

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