What should a constable do if they encounter a motorist suspected of driving with defective eyesight?

When a constable encounters a motorist suspected of driving with defective eyesight, the appropriate action is to carry out an eyesight test. This is because the constable needs to determine the motorist's ability to see adequately, which is critical for ensuring the safety of all road users. An eyesight test can provide concrete evidence of the motorist's visual capabilities and establish whether they pose a risk while driving.

Conducting an interview may gather information from the motorist, but it doesn't directly assess their eyesight. Issuing a warning does not address the potential danger posed by impaired vision while driving. Seizing the vehicle might be a drastic measure for the situation and is typically reserved for more severe violations or circumstances that pose an immediate danger.

Thus, the correct course of action centers around assessing the motorist's eyesight capability through a defined test, which is fundamental to enforcing road safety laws effectively.