Method and device for detection and assessment of marijuana impairment

• US 10,646,115 B2
• Filed: 09/05/2019
• Issued: 05/12/2020
• Est. Priority Date: 10/20/2015
• Status: Active Grant

• Current Assignee: Denise A. Valenti
• Original Assignee: Denise A. Valenti
• Inventors: Valenti, Denise A.
• Primary Examiner(s): Pinkney, Dawayne
• Application Number:
  US16/562,029
• Publication Number:
  US 20190387967A1
• Time in Patent Office: 250 Days
• Field of Search: 351239, 351200, 351205, 351246, 351221-222
• CPC Class Codes: A61B 3/0025 characterised by electronic signal processing, e.g. eye models
• CPC Class Codes: A61B 3/0041 characterised by display arrangements
• CPC Class Codes: A61B 3/02 Subjective types, i.e. testing apparatus requiring the active assistance of the patient
• CPC Class Codes: A61B 3/06 for testing light sensitivity, e.g. adaptation; for testing colour vision
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

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.

Claims

1. A method of identifying individuals impaired by a psychoactive substance other than alcohol, the method comprising:

presenting monocularly to a subject being tested;

to each eye separately, a pattern of fixed spatial frequency with achromatic contrast between dark areas and light areas, the achromatic contrast between the dark areas and the light areas 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 pattern thereby evaluating retinal function;

decreasing the contrast of the pattern presented until a first contrast ratio/value is reached wherein the frequency doubling in the pattern is no longer reported as being seen by the test subject;

further decreasing the contrast of the 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 pattern until a third contrast ratio/value is reached where the frequency doubling in the 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 the psychoactive substance and have no pathology impacting retinal 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.

2. The method as claimed in claim 1, further comprising varying the first contrast ratio/value identified and varying the temporally alternate modulation in a range from 10 Hz to 60 Hz and determining a frequency doubling value when the frequency doubling in the pattern is first detectable by the test subject.

3. The method as claimed in claim 1, further comprising varying the third contrast ratio/value identified and varying the temporally alternate modulation in a range from 10 Hz to 60 Hz and determining a frequency doubling value when the frequency doubling in the pattern is first detectable by the test subject.

4. The method as claimed in claim 1, further comprising comparing the frequency doubling temporal value values identified to the contrast ratio values combined with temporal values in the modulation (alterations) and comparing the frequency doubling temporal values to the temporal values of a normal population who have not consumed the psychoactive substance and have no pathology effecting the retinal visual functions tested.

5. The method as claimed in claim 4, further comprising comparing the frequency doubling temporal value values identified to the contrast ratio values combined with temporal values in the modulation (alterations) and comparing them to the temporal values of a normal population who have not consumed the psychoactive substance and have no pathology effecting the functions tested.

6. The method as claimed in claimed in claim 1, further comprising determining a threshold by a procedure based on Bayesian statistics including Zippy Estimation of Sequential Testing (ZEST).

7. The method as claimed in claimed in claim 1, further comprising presenting the pattern of fixed spatial frequency as an achromatic sinusoidal grating pattern.

8. The method as claimed in claim 1, further comprising holding the spatial frequency and the temporal frequency fixed while varying a contrast.

9. The method as claimed in claim 1, further comprising using a vehicle ignition interlock wherein if the test subject is found to be impaired the vehicle ignition interlock prevents operation of a motor vehicle.

11. The method as claimed in claim 7, further comprising presenting the sinusoidal grating patterns at an oblique angle to an ocular meridian.

12. The method as claimed in claim 7, further comprising presenting the sinusoidal grating patterns at a parallel or perpendicular to an ocular meridian.

10. A device for identifying individuals impaired by a psychoactive substance other than alcohol, the device comprising:

a display on which images are displayed monocularly to a subject being tested;

to each eye separately with achromatic contrast between dark areas and light areas, the display presenting a pattern of fixed spatial frequency with contrast between the dark and light areas 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 pattern thereby evaluating retinal function;

the display being coupled to a processor that is programmed with an algorithm by which an operator can control the display to present the following procedure;

decreasing the contrast of the pattern presented until a first contrast ratio/value is reached wherein the frequency doubling in the pattern is no longer reported as being seen by the test subject;

further decreasing the contrast of the 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 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 the psychoactive substance and have no pathology impacting the retinal 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.

13. The method as claimed in claim 10, further comprising obtaining biometric recognition wherein a user driving the vehicle is identified to be the test subject who took the test.

14. The device as claimed in claim 13, further comprising a vehicle ignition interlock wherein if the test subject is found to be impaired the vehicle ignition interlock prevents operation of a motor vehicle.

15. The device as claimed in claim 13, further comprising biometric recognition wherein a user driving the vehicle is identified to be the test subject who took the test.