What Causes Yellow Spot In My Daughters Vision?

Hi i have a 13 year old daughter who over a period of 4 years has experienced periodically yellow spots in her vision. She had lots of tests just for her vision and not medical. The visual disturbances lessened over a period of time however she still encounters them from time to time. In the last 2 years or so i have often been called to her school to pick her up as she goes very pale and feels dizzy and sometimes sick. She recovers within an hour or so. Whilst on holiday recently, my daughter got very dizzy, said she couldnt see properly, kept banging into thing then passed out on my. My husband took her off me and laid her on her back on the bed. Her eyes were fixed and staring into space and she briefly stopped breathing. We quickly picked her up and she started breathing again, she was very pale and had small droplets of perspiration on her face. She continued to feel faint and sick for around 10 minutes. Do you have any ideas on what this might be?

Thank you