The occipital lobes are the center of our visual perception system.

They are not particularly vulnerable to injury because of their location at the back of the brain, although any significant trauma to the brain could produce subtle changes to our visual-perceptual system, such as visual field defects and scotomas.

The Peristriate region of the occipital lobe is involved in visuospatial processing, discrimination of movement and color discrimination (Westmoreland et al., 1994). Damage to one side of the occipital lobe causes homonomous loss of vision with exactly the same "field cut" in both eyes. Disorders of the occipital lobe can cause visual hallucinations and illusions. Visual hallucinations (visual images with no external stimuli) can be caused by lesions to the occipital region or temporal lobe seizures. Visual illusions (distorted perceptions) can take the form of objects appearing larger or smaller than they actually are, objects lacking color or objects having abnormal coloring. Lesions in the parietal-temporal-occipital association area can cause word blindness with writing impairments (alexia and agraphia) (Kandel, Schwartz & Jessell, 1991).

References:

Kandel, E., Schwartz, J., & Jessell, T. Principles of Neural Science. 3rd edition. New York: NY. Elsevier, 1991.

Westmoreland, B. et al. Medical Neurosciences: An Approach to Anatomy, Pathology, and Physiology by Systems and Levels. New York: NY. Little, Brown and Company, 1994.