What are the possible causes for blindness?

Too many to list: There are too many causes to list for blindness. Most common causes are cataract, glaucoma, macular degeneration, and diabetic retinopathy. Search online for a more lengthy list.

So many possible : Light enters the eyes & is processed from the retina thru the optic nerve, then the "chiasm", then the "striations", to the back of the brain. Reversible blindness include cataract, corneal scars, certain retinal damage as causes. Optic nerve damage from glaucoma, toxin, ischemia, genetics; retinal damage from toxic, ischemic, scar causes, and congenital causes, degenerative disease (ms), rp, ...

Too many to mention: Cataracts, advanced glaucoma, macula degenerations. Any of a number of retinal disorders, including retinal detachment. Corneal scars, trauma......