Notes on Matching Eyeballs
Rather than picking up one eyeball at a time and pawing through a pile of eyes until I can find a mate, which leads almost directly to frustration, madness and eyestrain, some experimentation has yielded the following knowledge:
I found that the method that works the best for me involves a screen or hardware cloth stretched over the top of a box (although Target sells a wire mesh CD holder that works pretty well for this, too. It's also terrific for hanging earrings on!) Use a mesh size that will allow the eyeball to nestle nicely without falling through.
This essentially gives you something like a big piece of graph paper, like you used to draw graphs on in school.
Now, think of this grid as having two axes: moving in columns from left to right, the eyeball diameter increases; moving in rows from the bottom upwards, the pupil size increases. If you consider each eyeball to be a data point, start by taking one eyeball and plugging it into the grid where you think that the eyeball size (column) and pupil size (row) belong. This will be your starting point. Take the next eyeball and, if the eyeball size is larger, move it into a column to the right of the first eyeball; left if smaller. If the pupil size is larger, move it to a row in the same column that is above the first eyeball; a row somewhere below if the pupil is smaller.
Continue this method with each eyeball until you suddenly find two eyes that are sitting next to each other. There is your first pair! Continue this until all eyes have had a chance to pair up.
Each batch will probably wind up with a few oddballs, which are great in profile pieces, or saved to be matched up in future batches. (By the way: mismatched eyeballs are a great way to make a creature look like it has a concussion, or should otherwise have little birds or stars circling its head!)