Why does the narrator focus on the eye in "The Black Cat" ?

There can be many interpretations as to why the narrator
focuses on the eye of the cat in Poe's "The Black Cat". Here are a few of my own
interpretations.

First, Poe, himself, seems to have a
fascination with the eye. The imagery of the eye is not only seen in the story "The
Black Cat", but it is also depicted in the stories "The Tell-Tale Heart" (the narrator
is obsessed with the eye of the old man), "The Fall of the House of Usher" ("the vacant
and eye-like windows"), "The Gold Bug" (to find the treasure the left eye must be used),
"Dreamland" ("Weak human eye"), and "Hop-Frog" (how Hop-Frog's eyes change throughout
the story). Poe seems to know something about what the eye holds to include it in so
many of his works.

Secondly, to address one possibility as
to what the eye may mean for Poe is the old saying "The Eye is the window to the soul". 
This interpretation comes from Matthew 6:22-23 (King
James:

22 The
light of the body is the eye: if therefore thine eye be single, thy whole body shall be
full of light.

23 But if thine eye be evil, thy whole body
shall be full of darkness. If therefore the light that is in thee be darkness, how great
is that darkness!

This being
said, if Poe knew of the importance of the eye in detailing who a person is/was, he
would surely use the eye to denote its use to define a person or the person looking into
the eye of another.

As for "The Black Cat", the cat could
have "seen" who the narrator really was by looking in through his eyes. Frightened by
the thought of someone knowing his true self, the narrator took the eye of the cat so as
not to have any more of his soul revealed.

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The fury of a demon instantly possessed me. I
knew myself no longer. My original soul seemed, at once, to take its flight from my body
and a more than fiendish malevolence, gin-nurtured, thrilled every fibre of my frame. I
took from my waistcoat-pocket a pen-knife, opened it, grasped the poor beast by the
throat, and deliberately cut one of its eyes from the socket! I blush, I burn, I
shudder, while I pen the damnable
atrocity.

Another
interpretation of why the narrator took the eye of the cat can be his simple drunken
state and hate of the cat. The cat had just bit him and he retaliates by taking the eye.
Simplistic and boring and elementary, but another alternative.