Blindness and the Brain
How Blindness Affects the Structure of the Brain
What is Visual Impairment (Blindness) and how does it affect the structure of the brain?
Visual impairment refers to the loss of part or all of a person’s eye sight. This can be due to the damage of the eye, the optical nerves, or the visual cortex of the brain, or it can occur as a result of abnormal brain development. A number of conditions are associated with visual impairment. Regardless of the cause, visual impairment can lead to changes in how the brain structure develops.
Normally, visual images enter through the eye and travel the optic nerve into the visual cortex to be processed. When damage or developmental abnormalities are present that affect the visual process, the travel of these signals through the brain is impeded.
Structural changes in the brain related to uncorrected vision impairment, such as a loss of dendrite spines and a reduction of synapses as described in Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience by S. Marc Breedlove and Neil V. Watson, can occur resulting in the inability to transmit signals from the eyes to the visual cortex of the brain due to breaks in or incomplete neuropathways. Firing of nerves related to visual signals would not be able to completely travel the path to the visual cortex and other areas of the brain, resulting in the inability to process images. Early preventative measures and intervention can alleviate these issues, but if left unchecked until adulthood, most damage is permanent.
The above illustration shows the pathway for visual processing. Images are presented to the eye, which sends signals to the visual cortex to be processed. Damage or developmental abnormalities to any part or parts of these structures can lead to partial or total blindness.
This cross-sectional view of the brain shows how signals would travel from one eye or the other along opposing sides of the brain in a healthy person. Note that the pathway covers the entire length of the brain. Damage or developmental abnormality to seemingly any part of the brain could lead to some degree of visual impairment.
This illustration shows that more than just the visual cortex is necessary to process images. Signals sent from the visual cortex to other areas of the brain help us process images and answer questions such as "What is it?" and "Where is it?". This further shows that any number of interruptions in the brain could lead to the inability to process visual stimuli.