What causes ocular migraines and can they lead to blindness?

Ocular Migraines: Ocular migraines are caused by a very brief spasm of the artery that feeds the film layer of the eye (retina). This leads to the light flashes that you end up seeing in a classic migraine. It is rare to go blind from ocular migraines, but there is a risk of developing glaucoma with repeated bouts. You should see an eye doctor to evaluate you.

Migraine : Ocular migraine will not cause blindness. It has the same mechanism as regular migraine, the vessels involved are in vision cortex not in an area involved with nausea, vomiting or headache.

Reversible blindness: Retinal migraine is usually characterized by attacks of fully reversible monocular visual loss associated with migraine headache. Grosberg bm, solomon s, friedman di, lipton rb (2006) cephalalgia. 26 (11), 1275-86.