Believe it or not, complete loss of vision in one eye is often not obvious because dogs and cats are able to compensate very well using just the other eye. (healthypets.mercola.com)
It is usually short - lived and resolves itself, but in rare cases, it can cause complete loss of vision and even require removal of the affected eye. (vetinfo.com)
What they determined after further tests, however, was that she had multiple sclerosis, an autoimmune disease that affects the brain and central nervous system and was causing optic neuritis, an inflammation of the optic nerve that can cause a partial or complete loss of vision. (sciencedaily.com)