If you are highly near-sighted and are not wearing eyeglasses, then it might be a reason for your seeing things that are not there. It happens sometimes that a near-sighted person wrongly see something that are not there which is called an visual illusion. Another cause for visual illusion is that you are too fatigue and are using your eyes too much, therefore you might think that you see something but right away you realise that that thing is not there. At night, because the light is not as bright as in the day, it is more possible for you to have visual illusion. In this case, you had better go to wash your face and clean your eyes to make you feel more sober, and it may be better to lie down and close your eyes to have a rest. At ordinary times, you should pay attention not to overuse your eyes, and you had better do some eye exercises regularly and notice the cleaning job of your eyes.
