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Thread: HGN Horizontal Gaze Nystagmus

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    Question HGN Horizontal Gaze Nystagmus

    Does anyone have any info on the effects of glasses and/or hard or soft cl on this condition? ie can it be caused to any degree by glasses or cl wear?

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    Stick out tongue

    I haven't heard of spectacles or CLs having any affect on HNG. However, I do know that alcohol consumption does. Many police departments use an HNG test as part of their field sobriety testing. My ex husband used to be a cop and he was very good at guesstimating blood alcohol levels based on this test.

    Carol D:cheers:

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    I have seen a few cases particularly where albinism was involved with nystagmus that an opaque contact lens with a small puplillary opening would stop the condition while the lens was being worn.

    Chip

    Have not heard of a condition where refractive condition being corrected made the condition more appearent.

  4. #4
    Master OptiBoarder Joann Raytar's Avatar
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    From the website:
    http://www.nhtsa.dot.gov/people/inju...us/hgntxt.html
    Lack of equal tracking or equal pupil size may indicate blindness in one eye, a glass eye, a medical disorder or an injury.

    Nystagmus Caused by Non-Alcohol Related Disturbance of the Vestibular System

    Rotational nystagmus is caused by a disturbance in the inner ear fluid when a person spins
    around. The nystagmus lasts only as long as the person is being spun. If an observer could see a person's eyes while that person was spinning, a distinct jerking of the eye would be evident. Post-rotational nystagmus occurs after the person stops spinning. The nystagmus lasts for several seconds and can easily be seen.45

    Caloric nystagmus is caused by the movement of the inner ear fluid due to a difference in temperature of the fluid between the left and right ear. One way this can occur is if warm water is poured in one ear and cold water is poured in the other.46 Obviously this is an implausible scenario at roadside.

    Nystagmus Caused by Neural Activity

    Some types of nystagmus are caused by neural or muscle activity. Optokinetic nystagmus occurs when the eyes fixate on an object that moves quickly out of sight or passes quickly through the field of vision, such as occurs when a subject watches utility poles pass by while in a moving car. Optokinetic nystagmus also occurs when the eyes watch an object displaying contrasting moving images, such as black and white spokes on a spinning wheel.47 In either case, because the nystagmus is caused by the eye trying to catch up with the moving object, it lasts only as long as it takes for the object to stop moving, for the object to pass out of the field of vision, or for the eye to catch up to the object. Epileptic nystagmus is also a jerk nystagmus caused by neural activity that occurs primarily during epileptic or other types of seizures.48

    In addition, some people will exhibit a slight eye tremor when the eye moves to maximum deviation. This tremor is due mostly to eye strain rather than to any type of alcohol impairment or medical condition. When the HGN test is administered properly, a law enforcement officer cannot confuse this eye tremor with HGN due to alcohol impairment for several reasons. First, the eye tremor lasts only briefly and law enforcement officers are taught to hold the eye at maximum deviation for at least four seconds to ensure that the jerking is sustained. Second, the officer is looking for a distinct nystagmus, not a slight eye tremor. And finally, distinct nystagmus at maximum deviation is only one clue among the three the officer is looking for when checking for HGN.

    Nystagmus Due to Pathological Disorders

    Nystagmus may occur in people with brain damage, brain tumors or inner ear diseases. These disorders and others like them occur in a small number of the general population and even less often in drivers. Many of these alternative causes are so severe that it is unlikely that persons afflicted with the disorders would be driving, would not know they have the disorder or would be unaware of the effect the disorder has on their body. In addition, these types of nystagmus may be pendular rather than jerk nystagmus.
    Ahhh, the joys of spinning an infant on a stool and watching their eyes keep going bonkers after the stool stops spinning. Now you know why I don't have kids.

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