Q: I have had a problem with my eyesight. I have a delayed trail back vision when I look at lights or any moving object. It is more noticeable when I look at a light in a dark room. I will move the light around, for example in a figure 8 and it will form a perfect figure eight shape that I can clearly see for a while. Then it will slowly disappear. I have spoken to friends and family about the problem and they have told me everyone gets this very slightly but my problem is very, very noticeable and I am worried this could be a serious problem internally. Please advise.

A:I am pleased to say the symptoms you have are physiological i.e. normal, and this is called an 'after image'. It is also linked to dark adaptation ,in which, when you come from bright or day light to dim light, as in a matinee show cinema hall, your eyes take 10-15 minutes to recover. On the same principle, airline pilots have special goggles when landing on brightly lit runways, before and after which, they are in almost total darkness when they are flying in the sky. I can give you several examples like this, which can cause visual hallucinations.