Here is a complex representation of the eye. I have used a series of straight lines to "shade" in the iris. I tried to give the iris some blue color, but the black overshadows it too much. I also "shaded" the corners of the eye using dots. Finally, I darkened the lashes and gave them a bit more volume.

One of the biggest challenges for this composition was getting used to using software to create art. I am used to more traditional mediums of art, and so I really struggled to get the iris to look the way I imagined (making many straight lines is much faster and easier with pen and paper as opposed to software). I also had a hard time controlling how much color to put in the iris. I really wanted to use dots to represent the color, but the dots did not seem to show up enough against the black lines. And of course, I again had trouble making this composition more abstract. I guess I subconsciously associated "complex" with "detailed and accurate", and so I had a hard time making a complex representation also be abstract. That is definitely something I can work on.