Eye Examinations: Detecting Signs of Drug Influence

Eye Examinations:

Detecting Signs of Drug Influence

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B. Eye Examinations: Detecting Signs of Dug Influence

The eyes disclose some of the clearest signs of drug impairment or medical conditions.

• Horizontal gaze nystagmus is a very clear indication, in subject’s eyes, of possible

alcohol impairment.

• There are a number of drugs, other than alcohol, that will cause horizontal gaze

nystagmus.

• There are a number of other drugs that will not cause horizontal gaze nystagmus.

• There are many other clues that the eyes will disclose, all of which will suggest the

presence or absence of drugs or medical impairment.

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HS 178 R5/13 6 of 29

Session Overview – Introduction to Drugged Driving

DWI Detection and Standardized Field Sobriety Testing

Eye Examinations Overview

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The eye examinations that you can conduct

to assess possible drug or medical

impairment include:

• Resting nystagmus

• Tracking ability

• Pupil size

• Horizontal gaze nystagmus (HGN)

• Vertical gaze nystagmus (VGN)

Eye Examinations Overview:

The eye examinations that you can conduct to assess possible drug or medical

impairment include:

• Resting nystagmus

• Tracking ability

• Pupil size

• Horizontal gaze nystagmus (HGN)

• Vertical gaze nystagmus (VGN)

Resting Nystagmus is referred to as jerking as the eyes look straight ahead. This

condition is not frequently seen. Its presence usually indicates a pathological disorder or

high doses of a Dissociative Anesthetic drug such as PCP.

Tracking Ability will be affected by certain categories of drugs, and also by certain

medical conditions or pathological disorders.

If the two eyes do not track together, the possibility of a medical condition or injury is

present.

By passing a stimulus across both eyes, you can check to see if both eyes are tracking

equally.

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HS 178 R5/13 7 of 29

Session Overview – Introduction to Drugged Driving

DWI Detection and Standardized Field Sobriety Testing

Tracking ability will be affected by certain

categories of drugs, and also by certain

medical conditions or pathological

disorders

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Eye Examinations Overview (Cont.)

Tracking Ability will be affected by certain categories of drugs, and also by certain

medical conditions or pathological disorders.

If the two eyes do not track together, the possibility of a medical condition or injury is

present.

By passing a stimulus across both eyes, you can check to see if both eyes are tracking

equally.

If they don’t (i.e., if one eye tracks the stimulus, but the other fails to move, or lags

behind the stimulus) there is the possibility of a pathological disorder.

If a person has sight in both eyes, but the eyes fail to track together, there is a possibility

that the person is suffering from an injury or illness.

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HS 178 R5/13 8 of 29

Session Overview – Introduction to Drugged Driving

DWI Detection and Standardized Field Sobriety Testing

DWI Detection and

Standardized Field

Sobriety Testing

March 2013 Edition