Sorry to hear about your problem, and it sounds like you need to speak with a doctor
soon. The tunnel vision phenomenon, where things get harder and harder to see before everything goes black can sometimes be associated with a phenomenon known as a vasovagal reaction. It is something that can happen to people when they are scared, over stressed, in unusual situations, or overcome with emotion (sometimes referred to as the fainting
that happens when a person is scared, for example). That is a reaction that is somewhat common, and experienced by many people to one degree or another, but it is not something that should be dismissed. This loss of vision and light headed feeling is not something that should happen on a regular basis, and is something that needs to be discussed with a doctor to make sure that there is nothing wrong with your heart, your vascular system, or anything else. There are many different potential causes, and some of them can be quite serious and require urgent medical attention. Please speak with your doctor soon about your recent episode, and get the care you need before these events cause further problems.