What does it indicate if nystagmus is present before reaching 45 degrees?

The presence of nystagmus before reaching 45 degrees indicates a higher level of impairment and suggests potential alcohol influence. In the context of the Horizontal Gaze Nystagmus (HGN) test, trained officers look for specific markers of alcohol intoxication. Nystagmus is an involuntary jerking of the eyes, and when it is detected before the eye has reached the 45-degree angle, it signifies that the subject may have a blood alcohol concentration (BAC) at or above 0.08%, which is often the legal limit for driving under the influence. This physiological response occurs because alcohol affects the central nervous system and can impair eye muscle coordination. Thus, observing nystagmus at this angle is a strong indicator that the individual may be impaired, supporting the conclusion drawn from the results obtained during the HGN assessment.