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SFST Optometry Questions and Answers | Latest Version | 2025/2026 | Correct & Verified
What does HGN stand for in an SFST evaluation?✔✔ Horizontal Gaze Nystagmus
What eye movement does HGN testing look for?✔✔ Involuntary jerking of the eyes as they follow a moving object.
What is the primary cause of Horizontal Gaze Nystagmus during intoxication?✔✔ Central nervous system depression caused by alcohol or certain drugs.
Why must the stimulus be held 12-15 inches from the suspect’s face during HGN testing?✔✔ To ensure accurate observation of eye movement without strain or over-convergence.
What is equal tracking in an HGN test?✔✔ When both eyes follow the stimulus smoothly and at the same speed.
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What might unequal pupil size suggest during an SFST?✔✔ A possible head injury, neurological issue, or use of specific drugs.
What does lack of smooth pursuit indicate in an HGN test?✔✔ That the eyes do not follow the stimulus smoothly, suggesting impairment.
How many clues are observed during HGN testing?✔✔ A total of 6 clues, 3 per eye.
What is the “maximum deviation” during HGN testing?✔✔ When the eye is held at the far corner and observed for distinct nystagmus.
Why should the stimulus be moved slowly during HGN testing?✔✔ To give the eye time to follow naturally and to detect subtle jerking movements.
What does VGN stand for?✔✔ Vertical Gaze Nystagmus
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What does the presence of VGN usually indicate?✔✔ High doses of alcohol or certain central nervous system depressants.
Why must the suspect's head remain still during gaze tests?✔✔ Head movement can mask or mimic nystagmus, leading to inaccurate results.
What is convergence in an SFST eye exam?✔✔ The ability of the eyes to cross or come together when focusing on a near object.
What does lack of convergence potentially indicate?✔✔ Drug impairment, especially from certain CNS depressants or inhalants.
Why are optometric observations important during a field sobriety test?✔✔ They can reveal neurological impairment linked to substance use.
What is nystagmus?✔✔ An involuntary, rapid, and repetitive movement of the eyes.
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