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You will have noticed that one of the items in the checklist referred to mobility in dim light. If you found mobility to be poorer in dim light than in good light, you may wish to explore further the possible reason.
There is no hard and fast rule as to what is meant by dim versus good light. "Dim" does not mean "dark" - we all experience poorer mobility in a dark room! It is more of a qualitative judgment. If you and others get around easily in dim light but the learner's mobility is quite different from that in good light, there may be several reasons. If this has suddenly occurred you should investigate further.