Nystagmus among suspected amphetamine impaired drivers

Area of Science:

• Forensic Toxicology
• Clinical Pharmacology
• Ophthalmology

Background:

• Clinical signs of drug use aid in identifying consumed substances.
• Amphetamine intake has not traditionally been associated with nystagmus.
• Nystagmus is a subtest within the clinical test of impairment (CTI).

Purpose of the Study:

• To investigate the relationship between amphetamine use and nystagmus in apprehended drivers.
• To determine if nystagmus can be a clinical sign for amphetamine impairment in drivers.
• To compare nystagmus prevalence in amphetamine-only cases versus alcohol-only and drug-negative controls.

Main Methods:

• Evaluated drivers suspected of drug-impaired driving.
• Collected blood samples for alcohol and psychoactive drug analysis.
• Performed clinical tests of impairment (CTI), including nystagmus evaluation.
• Compared 507 amphetamine-only cases with 485 alcohol-only and 205 drug-negative cases.

Main Results:

• The proportion of cases with nystagmus was similar between amphetamine-only (21%) and drug-negative (25%) groups.
• Nystagmus was significantly more prevalent in alcohol-only cases (53%).
• No association was found between blood amphetamine concentration and the degree of nystagmus (p=0.860), but a significant association was found for alcohol (p<0.001).

Conclusions:

• Nystagmus is not a reliable indicator for identifying amphetamine impairment in drivers.
• The presence of nystagmus in apprehended drivers is more strongly associated with alcohol consumption.
• Clinical assessment for amphetamine impairment should not rely on the presence or degree of nystagmus.