This is my cross-sectional diagram of the human eye, created in Adobe Illustrator. My Clinical Sciences class had a guest lecturer come in from the University of Illinois Eye and Ear Infirmary. She gave to us all the information we needed to draft an accurate diagram of the eye, including all the measurements of each structure.
For the most part I used only line. I did sneak a gradient in there, in the posterior chamber, in order to clarify the surrounding anatomy. I made a few brushes as well to create tapered lines. For the vessels I used the pen tool, then outlined the strokes to vary the branch sizes.