I certainly don't want to worry you, but - in diabetics at least - such eyes-closed light-shows can be a sign of very low blood-glucose levels. Have you had any other actual eyesight problems recently? For example, is the far end of the High Street not quite as clear as it used to be? Been unusually thirsty of late? If so, I would certainly advise a visit to your GP. A website such as this is certainly not the place to seek advice about medical problems! I truly hope, therefore, that you have no such problems and that the other suggestions above are the reason for your "symptoms".