It is very important to see an ophthalmologist as this could be caused by localized bleeding, inflammation, swelling, retinal detachment, optic nerve problems. Find one at www.aao.org and go as soon as you can.
JCH MD
If this is something that lasts 10-60 minutes, it could be an ocular migraine. In any case, get it checked out by an ophthalmologist (MD eye doctor).
Nancy T.