My cousin sent me these images recently after he saw some magnified images of Isotelus trilobite fossil eyes showing the remains of the many lens that made up the eye. We are use to seeing this compound eye more on the Devonian Phacops trilobite fossils found in the area. He took some images under the microscope and you can see some of the lens pattern left on where the eye was.
This fossil dates to the Ordovician Period and was found in Franklin County Kentucky USA.
Thanks to Kenny for the images.