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Denise A Valenti, Chris Halsor, Dave Carbonetti; Acute Cannabis Use: Retinal Function. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5292.
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© ARVO (1962-2015); The Authors (2016-present)
Cannabis causes dysfunction in human retinal ganglion cells. We evaluated opportunistically; during vision screenings, seven participants who had acutely self-dosed with marijuana.
Two participants were seen at a health screening and evaluated only after acute marijuana use. The other five were seen at an event specific to cannabis. The event was a GreenLab under the direction “Undertanding Legal Marijuana, LLC”. These five were seen before and after marijuana use. GreenLabs are offered on a regular basis to train law enforcement specialists. Medical professionals took measures of heart rate, blood oxygenation and blood pressure from all participants. Three of the five participants visually screened had blood drawn to determine levels of tetrahydrocannabinol (TCH). The visual screenings incorporated a Zeiss 710 Frequency Doubling Technology (FDT) visual field test. FDT is often used for large group visual screenings and has been demonstrated to be reliable in young children as well as cognitively impaired adults. FDT uses a low spatial frequency grating of 10 degrees, presented at 1 of 16 test locations and tests the central forty degrees of vision. An addiitonal central target is 5 degrees. The grating alternates at 25 Hz. FDT has twelve reliability measures; six fixation tests, three false positive and three false negatives.
Among the group tested during the GreenLab were one non-chronic user and four long term chronic users. The two seen at a health screening were non-chronic users. All three of the non-chronic users had visual field defects measured in decibels in the superior field consistently, and defects sporadically elsewhere in all but the central region. The extent of the superior field defects was variable. The three non-chronic users had high reliability in the measures with each participant having one or fewer errors out of twelve. The pattern deviations measures were low among the non-chronic users. The long term chronic users had within normal findings measured in decibels. However, the reliability of all but one was unacceptable. The pattern deviations among the chronic, long term users were in the extreme elevated ranges in all but one.
Results show potential differences between long term chronic users and non-chronic users. An adaptation in chronic long term users may be scanning patterns that are enhanced. Or the brain has reorganized to adapt to the visual changes. Additional studies are warranted.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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