When one tries to meditate, the first obstacle in the beginning is sleep. When you get over this obstacle, there comes a condition in which, with the eyes closed, you begin to see things, people, scenes of all kinds. This is not a bad thing, it is a good sign and means that you are making progress in the Yoga. There is, besides the outer physical sight which sees external objects, an inner sight in us which can see things yet unseen and unknown, things at a distance, things belonging to another place or time or to other worlds; it is the inner sight which is opening in you. It is the working of the Mother’s force which is opening it in you, and you should not try to stop it. Remember the Mother always, call on her and aspire to feel her presence and her power working in you; but you do not need, for that, to reject this or other developments that may come in you by her working hereafter. It is only desire, egoism, restlessness and other wrong movements that have to be rejected.
Ref : Letters on Yoga Vol. III