I'm thinking you might have been told it was vasovagal syncope/syndrome. I attached a link. See if this is what they were talking about. It does in fact have triggers from OH, and POTS.

You should get a copy of the tilt table results and see exactly what they found in regards to your BP & heart rate and what caused your syncope/fainting.

You should also get a BP monitor and start taking measurements when you have symptoms and logging them. Most monitors also keep a history of readings. You can take the machine itself and show the doctor the history if there is significantly low BP's upon standing, etc. They also record heart rate.

I would ask for a full autonomic work-up to determine the cause of your passing out. The blurred vision is a common symptom with vasovagal syncope...so your symptoms seem to be related.

http://en.wikipedia.org/wiki/Vasovagal_response

Once they know the reason behind these episodes, there is a few possible treatments.