The poem's first line is as arresting as it is mysterious. The speaker tells the reader that they have had their "eye put out," meaning they have lost their sight. (Note that it's possible to take this literally—that the speaker has gone blind—or to read the speaker's "eye" as a metaphor for their awareness of the word, sense of self, or even their very life.)
The reader might well think that this is a pretty remarkable—and horrific—event, and justifiably want to know more. But the poem doesn't clarify what happened—or even who is speaking. The omission of such fundamental details ensures that the focus is not on the speaker's blinding, but on what they've discovered in their blindness.
Back in the sighted days, the speaker remembers being just like any other "creature" with eyes:
I liked as well to see
As other creatures, that have eyes —
And know no other way —
"Liked" here is an understated word, perhaps suggesting the speaker never really thought about what it meant to see when the seeing was good. In other words, the speaker took their vision for granted and didn't know any better. Their perception of the world was shaped by their sight and that was just the way it was. The mention of "creatures," as opposed to people specifically, suggests that taking seeing for granted is a natural, even instinctive state: animals do it as automatically as humans do.
Again, these lines might be read literally, but there are clearly some metaphorical possibilities here, too. Perhaps "seeing" here suggests the way that people experience the world in general—and the way that people take the world for granted. This poem will go on to explore what one can learn from losing one's everyday perceptions (and maybe even going beyond them).