Know that diabetes and retina detachment can cause blindness. But what else can cause blindness?

Very many things. There are probably hundreds of injuries and diseases that may cause blindness. Macular degeneration affects 10% of people over 80. Glaucoma risk increases with age. Cataracts can cause blindness if not treated. There are dozens of other neurologic, degenerative, hereditary, infectious, and traumatic causes of blindness, far too many to list here.