“Example, without a lens the eye doesn’t work as an eye, but it does work as a light dark detector.”
A poor example, because even the “light-dark” detector is incredibly complex and cannot form through mere random chance.
“When light first strikes the retina a photon interacts with a molecule called 11-cis-retinal, which rearranges within picoseconds to trans-retinal. (A picosecond [10-12 sec] is about the time it takes light to travel the breadth of a single human hair.) The change in the shape of the retinal molecule forces a change in the shape of the protein, rhodopsin, to which the retinal is tightly bound. The protein’s metamorphosis alters its behavior. Now called metarhodopsin II, the protein sticks to another protein, called transducin. Before bumping into metarhodopsin II, transducin had tightly bound a small molecule called GDP. But when transducin interacts with metarhodopsin II, the GDP falls off, and a molecule called GTP binds to transducin. (GTP is closely related to, but different from, GDP.)
GTP-transducin-metarhodopsin II now binds to a protein called phosphodiesterase, located in the inner membrane of the cell. When attached to metarhodopsin II and its entourage, the phosphodiesterase acquires the chemical ability to ‘cut’ a molecule called cGMP (a chemical relative of both GDP and GTP). Initially there are a lot of cGMP molecules in the cell, but the phosphodiesterase lowers its concentration, just as a pulled plug lowers the water level in a bathtub.” (M.J. Behe, Darwin’s Black Box: The Biochemical Challenge to Evolution (New York, NY: The Free Press, 1996), p. 46.)
And this is just one aspect of it, as issues such as location, or whether or not the creature can even understand the input, come into play next.
And evolutionists want us to believe, since they cannot find a single common ancestor for the eye, that this fantastic mechanism could be formed independently more than 30 different times in different species.
The eye is made of soft tissues that do not normally fossilize.
you mentioned that structures without one part were completely non functional. I showed that you were wrong, without one part, the eye is functional, just not functional as an eye. That means your argument of irreducible complexity is countered.