What does horizontal gaze nystagmus look like?

What does horizontal gaze nystagmus look like?

Horizontal gaze nystagmus refers to an involuntary jerking of the eyes as the eyes gaze toward the side. In addition to being involuntary, the person experiencing the nystagmus is unaware of its occurrence.

What can cause horizontal gaze nystagmus?

Police officers are concerned only with horizontal gaze nystagmus, a completely involuntary motion that becomes more pronounced when an individual is impaired by alcohol (in addition to some illicit and prescription drugs, primarily depressants).

How do you pass the horizontal gaze nystagmus test?


  1. Walk and Turn: Take nine heel to toe steps along a line (often an imaginary line, that the cop is imagining, not you!).
  2. One-Leg Stand: Stand on one leg for thirty seconds.
  3. Horizontal Gaze Nystagmus: Follow a stimulus (usually a finger or a pen) with your eyes without moving your head.

Is horizontal gaze nystagmus normal?

Purpose.: Physiologic gaze-evoked nystagmus (GEN) is one of many normal eye movements seen on the neurologic examination. GEN occurring at gaze angles >45° is considered a positive sign in the Horizontal Gaze Nystagmus Test (HGNT) used by United States police officers to determine alcohol intoxication.

What are the six clues for HGN?

HGN Cues/Clues of Intoxication There are a total of three clues that can be assessed in this test: lack of smooth pursuit, distinct nystagmus at maximum deviation, and the onset of nystagmus prior to 45 degrees. Each eye is scored independently for three clues in each eye giving a total of six indicators/cues.

What does horizontal nystagmus indicate?

Jan. 11, 2022. Nystagmus is a condition where the eyes move rapidly and uncontrollably. They can move: side to side (horizontal nystagmus)

How many clues are in horizontal gaze nystagmus?

six clues
Horizontal Gaze Nystagmus There are six clues, or three in each eye: Lack of smooth pursuit. Distinct and sustained nystagmus at maximum deviation. Onset of nystagmus prior to 45-Degrees.

What are the 3 clues in HGN?

How accurate is the HGN test?

NHTSA analyzed the laboratory test data and found: HGN, by itself, was 77% accurate. WAT, by itself, was 68% accurate.

How accurate is the horizontal gaze nystagmus test?

The horizontal gaze nystagmus test is only accurate in about 77% of cases. Reasons for a failed test could include: You suffer from a natural nystagmus in your eyes. You have the flu or an inner ear infection.

What neurological causes nystagmus?

What causes nystagmus? Jerk nystagmus usually results from diseases affecting the inner ear balance mechanisms or the back part of the brain (brainstem or cerebellum). Pendular nystagmus can result from brain diseases such as multiple sclerosis, but can be a congenital problem as well.

What is horizontal nystagmus?

Nystagmus is a condition where the eyes move rapidly and uncontrollably. They can move: side to side (horizontal nystagmus) up and down (vertical nystagmus) in a circle (rotary nystagmus)

What does an officer look for during the horizontal gaze nystagmus field sobriety test?

The Horizontal Gaze Nystagmus (HGN) Field Sobriety Test checks your eyes for involuntary jerking as you gaze to the side. The test begins by the police officer placing the tested person in the instructional stance where the feet are placed together and the arms are kept to the side.

Why does alcohol cause HGN?

These hinder the brain’s ability to properly control the eye muscles. The presence of such alcohol or drugs in the body’s system results in jerking or bouncing movements in the eyeball. The higher a person’s blood alcohol content level, the more obvious the nystagmus becomes.

Does HGN work for drugs?

HGN alone had an overall accuracy above chance for all drugs and categories of drugs except marijuana (THC) and any combination of one or more drugs. Note that drugs that are not expected to exhibit HGN, like cocaine, may be found in cases where other drugs causing HGN are present.

What is the horizontal nystagmus test?

What are the six clues in HGN?

Does caffeine cause HGN?

Caffeine can also cause the eyes to move more rapidly than usual, which could cause a failed HGN test.

Do sober people have nystagmus?

Most sober people have little or no HGN until they look all the way to the far left or far right, as far as the eye can move. Even then, a sober person typically has only faint nystagmus. When someone has been drinking, however, they exhibit more HGN.