Hi!
One of the problems I see here are that the lines are pretty rough in a few areas. That is, they look very jagged. At the lower left, it's most prominent. Try keeping the 2px tall blocks together, rather than separated by a few lone pixels at a time. You've also overdone the AA. Most of the time, a single pixel buffer should do, unless the segment is particularly long. You also likely only need 1 color for AA.
Now, about your colors. It's a little hard to tell them apart at 100% scale. I suggest using colors farther apart from each other for more contrast. On the other hand, the black outlines really stick out. You might want to use a dark, unsaturated color other than black.
Finally, the shading. I agree with Quake in that it would be better for you to study up on imagining your works in 3D. The shading looks a little flat, and not like the eye is a sphere-ish object.
All that said, trying as much as possible to maintain the style you were going for, I've made an edit applying some of my suggestions:
Good luck, and cheers ^^