If i had brain tumor and it was effecting vision would my dr see pressure on my optic nerve?

Maybe not: Some brain tumors do not put any pressure on the optic nerve. On the other hand, there are lots of other causes of vision problems. It is probably not worthwhile jumping to conclusion that your vision problem is caused by a brain tumor.

Not necessarily: If there is increased pressure in the brain, from a tumor or other reasons, you can have optic nerve swelling, called papillaedema.