Its complex structure includes the lens, cornea, retina, optic nerve, pupil, iris and much more. All of these components work together to provide necessary function of our vision, and make the eyes performance irreducibly complex.
For instance, glaucoma and blindness can result if proper fluid pressure in the vitreous humor (clear jelly behind our lens) is not adjusted. Or, if the eye lens were cloudy, it would be subject cataracts and the inability to see.
Each part of the eye had to be set in place and fully functional from the start in order for the eye to operate and its complicated blueprint could not happen by chance!