Method and device for detection and assessment of marijuana impairment

Abstract

A method of identifying individuals impaired by a psychoactive substance such as cannabis. The method includes presenting monocularly to a subject being tested; to each eye separately, a sinusoidal grating pattern of fixed spatial frequency with achromatic contrast or color contrast between grating stripes being temporally alternately modulated at a temporal frequency that ranges between 10 Hz and 60 Hz with a pattern of the contrast being such that the subject being tested can see a frequency doubling in the grating pattern.

1 . A method of identifying individuals impaired by a psychoactive substance, the method comprising:
 presenting monocularly to a subject being tested; to each eye separately, a sinusoidal grating pattern of fixed spatial frequency with achromatic contrast or color contrast between grating stripes, the achromatic contrast or the color contrast between the grating stripes being temporally alternately modulated at a temporal frequency that ranges between 10 Hz and 60 Hz with a pattern of the contrast being such that the subject being tested can see a frequency doubling in the grating pattern;   decreasing the contrast of the grating pattern presented until a first contrast ratio/value is reached wherein the frequency doubling in the grating pattern is no longer reported as being seen by the test subject;   further decreasing the contrast of the grating pattern until a second contrast ratio/value is below the test subject's threshold of detection of the second contrast ratio/value;   increasing the contrast of the grating pattern until a third contrast ratio/value is reached where the frequency doubling in the grating pattern is first detectable;   comparing the first contrast ratio/value and the third contrast ratio/value to a range of expected values of a normal population who have not consumed cannabis and have no pathology impacting the visual functions tested;   if the first contrast ratio/value and the third contrast ratio/value are within the range of expected values, then indicating that the test subject is not impaired; and   if the first contrast ratio/value and the third contrast ratio/value are not within the range of expected values then indicating that the test subject is impaired.