Whitman is basically referring to like the negative feelings/ darkness that's over coming him and the way he describes it you can tell he wants to be free from it.

Right here what I took from it was that although she was talking about the window, the window was resembling her eyes and not only about how they closed but also how she might have felt disconnected from the outside world. Another thing I referenced was that since sometimes people say that "eyes are the windows to the soul" I feel like she indirectly played off of that as well.