In which testing condition is the Horizontal Gaze Nystagmus test typically conducted?

The Horizontal Gaze Nystagmus (HGN) test is typically conducted in a dimly lit area to allow for an optimal assessment of the subject's eye movements. This controlled lighting condition is crucial because it helps to enhance the visibility of nystagmus, which is an involuntary jerking of the eyes that becomes more noticeable under such lighting.

Conducting the test in bright sunlight or intense light can create glare or reflections that may interfere with the observer's ability to clearly see the eye movements, leading to potential misinterpretation of the results. On the other hand, performing the test in total darkness would render the evaluation ineffective, as the officer would not be able to see the subject's eyes at all. Therefore, a dimly lit environment strikes the right balance, allowing the examiner to observe and accurately interpret the nystagmus response during the HGN assessment.