ArticleBMC ophthalmology2025
Effects of intravenous d9-THC on pupillary reaction and pupil size: a prospective, placebo-controlled trial in healthy volunteers not regularly consuming cannabis.
Article in BMC ophthalmology, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
introductionThis prospective, single-blind, placebo-controlled trial examined the effects of intravenous delta-9-tetrahydrocannabinol (d9-THC) on the pupillary light reflex and pupil size in volunteers not regularly consuming cannabis.
methodsWith ethics committee approval and written informed consent, healthy cannabis-naïve or abstinent volunteers were included. Fifteen volunteers received an intravenous bolus of d9-THC and four received placebo. Pupillary reaction and pupil size were assessed by pupillography before and for 5 h after drug administration. Primary outcome was relative amplitude. Secondary outcomes were latency, velocity of contraction, constriction time, contraction amplitude, and pupil diameter.
resultsPupillographic measurements were significantly altered by THC: The relative amplitude was significantly reduced with a global difference between groups (p = 0.001). The relative amplitude significantly declined at 20 min after THC administration (23.5-15.0%), and stayed constant in after placebo (27.5-28.1%). Constriction time was significantly reduced with a significant global time effect (p = 0.002), global group effect (p = 0.001), and global effect of the interaction between group and time (p < 0.001). Contraction amplitude was reduced with a significant global group effect (p < 0.001). Latency and velocity of contraction demonstrated a statistically non-significant increase. Pupil size decreased after THC administration. DISCUSSION: Pupillography can objectively detect effects of THC on the human eye. In cannabis-naïve or abstinent volunteers THC dampens the pupillary light reflex which could result in an increased sensitivity to light. THC does not cause mydriasis, but rather miosis. These results can substantiate questions regarding liability and driving ability under the influence of THC.
trial registrationThe study was prospectively registered at www.isrctn.com (registration number ISRCTN53019164) on 14/04/2010.
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