Final answer:
The vision problem not associated with a driver under the influence of alcohol is focus drifting towards the horizon. Alcohol can cause a tunnel vision effect, leading to impaired peripheral vision and decreased awareness of the surroundings.
Step-by-step explanation:
The problem that was not associated with the vision of a driver under the influence of alcohol is C. Focus drifting towards horizon. When a driver is impaired by alcohol, their central vision can become overly focused on a specific area, such as the road, leading to a type of tunnel vision where peripheral details may be missed. This impairment is due to the effects of alcohol on brain regions like the cerebellum which impacts coordination and motor control, including the control of eye movements. This can make it difficult for an intoxicated driver to notice stimuli off to the sides, which is a serious safety concern.