Eyes have evolved separately at least 40 times. In none of these instances has it ever been necessary for a whole eye to evolve in one gigantic evolutionary leap.
Being sensitive to light is extremely important from a survival point of view - it enables animals to detect food and/or avoid predators. Even the smallest degree of sensitivity to light gives an advantage over a rival or predator with less sensitivity.
Eyes evolved through a continuum of small modifications and improvements from simple light sensitive spots within a cell to a single light-sensing cell, to a flat patch of light sensing cells to a cup-shape of light sensing cells (or ball-like curve in some instances, such as insects). From unfocussed to fixed focus to variable focus. From immobile to moveable. From monochrome vision to dichromatic all the way to four-colour vision as seen in turtles. The animal kingdom exhibits all forms of eyes and it is possible to trace the evolution of many of them.
The human eye actually provides excellent evidence in support of evolution:-
1. the nerves linking the light-sensitive cells to the brain lead out the front of the retina, thus partially obstructing the light heading towards the cells. This is the reverse of intelligent design and goes part-way to explaining why human (and other mammal) eyesight is poorer than other groups of animals such as octopus and squid where the nerves feed out the back of the cells. The mammal design is a result of the way the retina first evolved millions of years ago.
2. Humans only see in three colours (trichromatic vision). Many of our ape relatives and ancestors only see in two or even one colour as colour vision was much less important in low-light conditions, demonstrating that our ancestors were nocturnal. We have partially regained our colour vision by mutation of one gene which became duplicated. This can be traced through living descendants of our primate ancestors such as chimps and gibbons and permits us to calculate when the mutation ocurred and how the various groups of primates are inter-related.
Your argument that just because intermediate stages are not now in existence somehow supports the notion that the whole thing had to be created at once is a nonsense. A stone arch bridge requires all its constituent parts to function - remove just one and the arch collapses. Yet the bridge exists (without the help of god). This is because a frame was first constructed on which the arch was built, the frame subsequently being removed as unnecessary. The same applies to complex organs such as eyes, ears, liver, kidneys etc etc.
The fact that you cannot understand how things evolved does not in any way imply that they had a supernatural or godly origin but merely that you are deliberately or otherwise poorly educated.
UPDATE: I'm afraid your professor - whoever he is - is very much in the minority or scientists, most of whom are fully aware of the fallacy of irreducibility. Of course an eye functions without a lens. Some primitive eyes have no lens even today - simple cup0shapes of light-sensitive cells function perfectly well without a lens. A pin-hole camera also functions perfectly well without a lens.
Natural selection does not "choose" but it does favour by removing those forms which are less efficient. If mammals had been competing directly against squid in an environment where acute vision was at a premium then mammals may have become extinct. Natural selection has no conscious direction and cannot be reversed, only incrementally modified. The principle of the stone arch applies to all organs and forms and it is only your willful incredulity which prevents you from seeing what is obvious from the evidence.
You really should get a better education.