Why do i loose my vision when i black out?

Why blacking out?: The vision and brain are very sensitive to blood flow and oxygen levels in the blood. People are very attuned to their vision, so changes there are often noticed first. Visual symptoms before blacking out can include dimming of the vision, loss of peripheral or central vision, waviness of the vision, and then finally loss of vision. Why are you having black outs? That should definitely be checked.

Lack of blood supply: The eye needs a good blood supply and most black outs are like fainting in which the blood pressure drops and you lose consciousness. At your age what are you doing to cause this? If these are spontaneous, then you should see your family doctor for evaluation.