What is the 3rd clue for impairment?

What is the 3rd clue for impairment?

• A. Onset of nystagmus prior to 45 degrees
• B. Onset of nystagmus at 60 degrees
• C. Nystagmus only after 60 degrees
• D. No nystagmus observed

Answer: (A)

In the Horizontal Gaze Nystagmus test, three cues indicate impairment. The third clue is when nystagmus appears before the eyes reach 45 degrees of lateral gaze. Normally, smooth pursuit can be maintained up to about 45 degrees, so seeing a distinct nystagmus earlier signals that the brain’s eye-movement control is affected, which points to impairment. The other possibilities describe signs that occur at or after 60 degrees or not at all, which do not match this early-onset cue. So the onset of nystagmus prior to 45 degrees is the correct indicator.

In the Horizontal Gaze Nystagmus test, three cues indicate impairment. The third clue is when nystagmus appears before the eyes reach 45 degrees of lateral gaze. Normally, smooth pursuit can be maintained up to about 45 degrees, so seeing a distinct nystagmus earlier signals that the brain’s eye-movement control is affected, which points to impairment. The other possibilities describe signs that occur at or after 60 degrees or not at all, which do not match this early-onset cue. So the onset of nystagmus prior to 45 degrees is the correct indicator.