Here is a picture of one of the creatures found in the Cambrian explosion – a trilobite. Many thousands of fossils of fully-formed trilobites are found without a trace of simpler ancestors. And these creatures are not simple by any definition. In fact, the eye of the trilobite is very complex and unique, being made of inorganic calcite.
From The Amazing Story of Creation, p. 104:
The first significant thing about these eyes is that they have a double lens. Each one of our eyes has only a single lens. In order to see under water without distortion, however, you must have double lens in each eye, and that is precisely what the trilobite had. The most incredible thing about the trilobite eye, however, is the fact that it produced perfect, undistorted vision. Dr. Levi-Setti discovered that the trilobites had “solved” Abbe’s Sine Law, Fermat’s Principle, and other laws and principles of optics, and had perfectly constructed crystalline lenses so that there was no distortion at all. The scientists studying these eyes proclaimed that these eyes looked as if they had been designed by a physicist!