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If you are looking at a spot on the wall it is no more dangerous to your vision that any point source of light would be. Since the dot can be seen from anywhere in the room, it follows the inverse square law. This states that the intensity of light decreases as the square of the distance you are from it divided into 1. This does not apply to a collimated beam reflection as that cannot be seen as a point source from anywhere in the room. Even bright sources of laser light on a wall, while uncomfortable will not cause you harm just like the flash from a camera may cause you some discomfort and immediate decrease in visual acuity, but then gets normal again after a short period of time.