Is it possible to permanently lose my vision from a corneal ulcer?

Absolutely: Especially if it is the central cornea and/or if it is not adequately treated in time with medications. Sometimes the damage is extensive and requires a corneal transplant.

Yes, but rare: If the organism causing the corneal ulcer is an aggressive bacteria, fungus, or protozoa, permanent corneal scarring can result. Even corneal perforation can take place with loss of an eye. These are serious infections and require ophthalmologic care.