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Eye Tracking as a Biomarker of Cannabis Effects

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ClinicalTrials.gov Identifier: NCT04100590
Recruitment Status : Active, not recruiting
First Posted : September 24, 2019
Last Update Posted : October 1, 2020
Sponsor:
Information provided by (Responsible Party):
Caroline A. Arout, Ph.D., New York State Psychiatric Institute

Brief Summary:

Biomarkers of recent drug use and intoxication have societal relevance, in that they are used by law enforcement and other agencies to detect drug impairment. For instance, a breathalyzer can quickly and accurately detect blood alcohol content (BAC) to indicate if a person is under the influence of alcohol; however, there is currently no similar way to quickly detect if a person is under the influence of cannabis. In light of increasing cannabis use, it is important to define a quantitative, objective method of determining recent use and intoxication.

The link between changes in eye characteristics (e.g. movement, pupil dilation) and cannabis use is documented (Peragallo et al. 2013), but insufficiently characterized. Certain outcomes of eye behavior are known to be affected by recent cannabis use (e.g. the eyes' ability to converge on a target; Stapleton et al 1986), while findings are mixed regarding other outcomes (e.g. the eyes' ability to smoothly follow a target; Fant et al. 1998). Thus, the goal of this study is to identify a characteristic pattern of eye behavior, defined by performance on a battery of four eye tasks, as a function of recent cannabis use (7% vs. 0% THC).

Using 30 healthy cannabis users (15 men, 15 women), this study will be one of the first to assess changes in eye behavior as a function of recent cannabis use within a quantified virtual reality (VR) environment. This study will examine the effect of smoked cannabis (7% vs. 0% THC) on individual eye movements, with the goal of defining the utility of the eyes as potential objective indicators of cannabis use and intoxication. Four eye tests (nystagmus, smooth pursuit, convergence, and pupillary light response; outlined below), which previous literature has defined as effective in detecting recent drug use (including opioids and alcohol; Murillo et al. 2004), have been compiled into a 5-minute task battery using a VR headset environment equipped with high frequency infrared eye trackers (the HTC Vive with Pupil Labs Tracking). This 5-minute VR battery of four eye tests will be administered prior to cannabis consumption as a baseline, and then at 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 min after cannabis, with the goal of comparing baseline values to the ten post-cannabis timepoints to detect changes in eye behavior as a function of cannabis intoxication. The study will also utilize a battery of subjective-effects and mood visual analogue scales (0-100 mm; e.g. 'Good Drug Effect') prior to the eye test battery at each timepoint, allowing us to correlate each outcome of the eye tasks to subjectively reported cannabis impairment and mood.

In addition to measuring eye behavior as a function of cannabis use, the training session of this study will be used to also collect exploratory data on the relationship between pupil dilation and experimental pain. Using Quantitative Sensory Testing (Medoc TSA-II NeuroSensory Analyzer), thermal pain threshold and tolerance will be induced using a cold stimulus (4.0°C; induced with a 30 x 30 mm Peltier thermode, which is 1.5" square metal applicator that is connected to the TSA-II NeuroSensory Analyzer device and software, and produces an ongoing cold sensation applied to the lower palm of the participant's non-dominant hand). Participants will indicate first feelings of pain (pain threshold), and when the pain becomes too much to bear (pain tolerance) by pressing a button on a controller connected to the TSA-II. Throughout exposure to the cold stimulus, changes in pupil size to the patient's subjectively reported pain latencies will be recorded.


Condition or disease Intervention/treatment Phase
Cannabis Use Pain, Acute Drug: Cannabis Phase 2

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 1 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Intervention Model Description: Each volunteer will participate in two sessions in a cross-over fashion (active cannabis vs. inactive placebo cannabis)
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Basic Science
Official Title: Eye Tracking as a Biomarker of Cannabis Effects
Actual Study Start Date : October 1, 2019
Estimated Primary Completion Date : September 30, 2021
Estimated Study Completion Date : September 30, 2023

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Marijuana

Arm Intervention/treatment
Experimental: Active Cannabis
In this session, the participant will smoke two-thirds of one active cannabis cigarette (7% THC) according to our paced-puff procedure (Foltin et al. 1987). They will complete an eye task battery (5 minutes per battery) 15 minutes prior to smoking as a baseline measure in each session, and again at the following timepoints: 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis. Baseline assessments will be compared to those at post-cannabis timepoints.
Drug: Cannabis
Smoked active cannabis (7% THC) vs. placebo inactive cannabis (0% THC)

Placebo Comparator: Placebo Cannabis
In this session, the participant will smoke two-thirds of one inactive placebo cannabis cigarette (0% THC) according to our paced-puff procedure (Foltin et al. 1987). They will complete an eye task battery (5 minutes per battery) 15 minutes prior to smoking as a baseline measure in each session, and again at the following timepoints: 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis. Baseline assessments will be compared to those at post-cannabis timepoints.
Drug: Cannabis
Smoked active cannabis (7% THC) vs. placebo inactive cannabis (0% THC)




Primary Outcome Measures :
  1. Horizontal Gaze Nystagmus (HGN) [ Time Frame: % Change from baseline during each of two sessions (measurements taken at baseline, 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis) ]
    Using a Virtual Reality headset, a stimulus (a fixation cross) moves from the center of the visual field to 45 visual degrees to the right and left and is held at each extreme for 10 seconds. The accuracy with which the participant completes this task will be measured by comparing pupil position with the target position within the virtual reality environment, down to the millimeter. Speed will also be assessed by measuring pupil position as a function of target fixation, down to the millisecond.

  2. Vertical Gaze Nystagmus (VGN) [ Time Frame: % Change from baseline during each of two sessions (measurements taken at baseline, 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis) ]
    Using a Virtual Reality headset, a stimulus (a fixation cross) moves from the center of the visual field to 40 visual degrees up and down and is held at each extreme for 10 seconds. The accuracy with which the participant completes this task will be measured by comparing pupil position with the target position within the virtual reality environment, down to the millimeter. Speed will also be assessed by measuring pupil position as a function of target fixation, down to the millisecond.

  3. Smooth Pursuit (SP) [ Time Frame: % Change from baseline during each of two sessions (measurements taken at baseline, 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis) ]
    Using a Virtual Reality headset, a stimulus (a fixation cross) moves from each extreme of the visual field at a speed of 40 degrees/second. This test measures the tracking ability of the eyes. The smooth pursuit test is embedded in the nystagmus tests; it takes place in between the HGN/VGN tests as the stimulus moves from the horizontal/vertical extremes. Horizontal smooth pursuit is assessed as the stimulus moves from one side of the visual field to the other, while vertical smooth pursuit is assessed when the stimulus moves from the upper extreme of the visual field to the lower extreme, or vice versa. The accuracy with which the participant completes this task will be measured by comparing pupil position with the target position within the virtual reality environment, down to the millimeter. Speed will also be assessed by measuring pupil position as a function of target fixation, down to the millisecond.

  4. Convergence [ Time Frame: % Change from baseline during each of two sessions (measurements taken at baseline, 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis) ]
    Using a Virtual Reality headset, a stimulus (a fixation cross) moves from 12 inches to 2 inches away from the participant's nose at a continuous speed over 5 seconds, then is held at that point for 10 seconds. The accuracy with which the participant completes this task will be measured by comparing pupil position with the target position within the virtual reality environment, down to the millimeter. Speed will also be assessed by measuring pupil position as a function of target fixation, down to the millisecond.

  5. Pupillary Light Reflex (PLR) [ Time Frame: % Change from baseline during each of two sessions (measurements taken at baseline, 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis) ]
    Using a Virtual Reality headset, a bright light is presented in a previously dark setting for 10 seconds followed by 30 seconds of no light for pupil adjustment. Size and speed of pupil constriction will also be assessed (in millimeters and millisecond, respectively).

  6. Pupillary Light Flash Reflex (PLFR) [ Time Frame: % Change from baseline during each of two sessions (measurements taken at baseline, 0, 15, 30, 45, 60, 75, 90, 105, 120, and 165 minutes post-cannabis) ]
    Using a Virtual Reality headset, a light is flashed once for one second followed by an observation period of 5 seconds. During the observation period, no lights flash and the participant's reaction to darkness is assessed. Size and speed of pupil constriction will also be assessed (in millimeters and millisecond, respectively).


Secondary Outcome Measures :
  1. Quantitative Sensory Testing Thermal Pain (QST-TP) [ Time Frame: 1 time at Screening ]
    A thermal testing analyzer (Medoc TSA-II NeuroSensory Analyzer) with a 30 x 30 mm Peltier thermode is used to apply a cold stimulus on the thenar eminence of the palm. The temperature is set to 4.0°C. Using a computerized response button, participants will note the time (in seconds) at which they begin to perceive the cold as painful, and when it becomes too painful to continue. At this latter point, the program will discontinue the cold stimulus and return to baseline temperature. Participants also continuously rate the magnitude of perceived pain using a computerized Visual Analog Scale (Co-VAS, a range of 0-100mm; 0=no pain, 100=worst pain imaginable) throughout stimulation. Throughout this assessment, changes in pupil dilation will be measured using the eye-tracking headset and correlated to their subjective Co-VAS pain responses. If participants exceed the 3-minute cut-off, the task will be discontinued in order to avoid tissue damage.



Information from the National Library of Medicine

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Ages Eligible for Study:   21 Years to 55 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Males/non-pregnant females
  • Report smoking cannabis ≥1 day per week
  • Able to perform all study procedures

Exclusion Criteria:

  • Meeting DSM-V criteria for severe substance use
  • Use of illicit drugs ≥1 day/week in the prior 4 weeks
  • Abnormality with the eyes which may affect the eye tracking technology such as color blindness, naturally occurring nystagmus, amblyopia, strabismus, age-related macular degeneration (AMD), cataract, diabetic eye disease, glaucoma, dry eye, extreme refractive error, bacterial or viral infections of the eye
  • 7. User of supplemental oxygen

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT04100590


Locations
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United States, New York
New York State Psychiatric Institute
New York, New York, United States, 10032
Sponsors and Collaborators
New York State Psychiatric Institute
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Responsible Party: Caroline A. Arout, Ph.D., Assistant Professor of Neurobiology, New York State Psychiatric Institute
ClinicalTrials.gov Identifier: NCT04100590    
Other Study ID Numbers: 7844
First Posted: September 24, 2019    Key Record Dates
Last Update Posted: October 1, 2020
Last Verified: September 2020
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Undecided
Plan Description: De-identified eye-behavior data will be available to other researchers.

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Studies a U.S. FDA-regulated Drug Product: Yes
Studies a U.S. FDA-regulated Device Product: No
Additional relevant MeSH terms:
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Acute Pain
Marijuana Abuse
Substance-Related Disorders
Chemically-Induced Disorders
Mental Disorders
Pain
Neurologic Manifestations