Don't assume the person understands. Watch to see what the person does, rather than trusting what he or she says. Impaired people frequently become very skillful at concealing the fact that they do not understand. If you suspect that the person does not get what you mean, try to find a new, simpler way to express the same idea. Living with the problem Vision problems in a dementia person may make caregiving a harder task.
Safety becomes a bigger concern.
You may have to modify the environment and watch the person more closely. The caregiving task can tire, frustrate and upset you. The impaired person may sense this and also become upset. This can make your job even harder. You will need to develop techniques for coping with both.