How We See
When we observe an image, light reflects off the object thus portraying the image as our eyes interpret the reflected light. As the is reflected back, due to the change in refractive index from the air to the cornea and the biconvex nature of the lens within the eye as seen in Figure 1, the light bends in towards the iris, thus converging at the Retina.
The retina is a membrane containing the photoreceptor nerve cells which convert the light rays into electrical impulses. These electrical impulses are then sent through the optic nerve to the brain, where an image is then perceived.