The optic nerve that connects your eye to the brain translates images seen into electrical impulses. These impulse signals travel down the optic nerve to the area of your brain known as the visual cortex (I've never heard it referred to as the visual "association" cortex). If the visual cortex is damaged, the impulses can not be integrated and thus will not be perceived by the brain as they really are. For instance, images could appear misshapen (metamorphopsia) or flashes (photopsia) could be present. There is a lot more that could be manifested by such an injury but you get the idea.
