What Causes Blurred Vision Along With Dizziness?

I can be sitting down or standing and all of a sudden my vision will become blurred as well as a warm feeling comes over me and sometimes I have experienced it as well as being light headed. This does not happen often and by often I mean I can go months without this experience but when it does happen it concerns me because I know my body is trying to tell me something..Just don't know what it could be..Help.