Henry Drummond in his well-known book, Natural Law in the Spiritual World, tells of a fish that lives in the subterranean lakes of Mammoth Cave. These caves are so deep below the surface that no ray of natural light ever gets into them. In other words, the fish has existed in absolute darkness for centuries.
The most interesting thing about the fish is that it has eyes. Yet, it cannot see. Through the years the optic nerve atrophied until vision was no longer possible.
I know people like that. They have eyes and they can physically see, but they do not have the capacity to vision.
Conversely, I have known people who were physically blind but who had tremendous sensitivity and vision about emotional and spiritual realities. Some of the greatest poets that have ever lived were physically blind.
The most famous person to have ever lived used to say of people, "You have eyes to see but you can't see."