Initially, it might be little greater than simple pattern recognition. Biological vision utilizes massively parallel analog processors, usually called nerve cells, which combine output to extract from the visual field such details as edges, local contrast, and movement. Odd as it may sound, we do not see the world as it really is. Using only a fragment of the total electromagnetic spectrum available, from reflected wavelengths we impute to objects completely subjective properties like color and texture. Long before the visual input gets to our brain, the data have been processed to make edges edgier, and contrast more visible.
Movement is given special attention, especially in our peripheral vision.
Neuromorphic chips try to implement this biological signal processing in silicon. The brain doesn't want to use a lot of wire, either. Unlike a camera which whites out the image in the presence of too much light, the eye is capable adjusting to logarithmic changes in light intensity. So too with Delbruck's neuromorphic photoreceptors which uses silicon transistors to accomplish the same thing. In the silicon retina, logarithmic photoadaptors are connected to a two dimensional analog grid, using design principles of the natural retina.