Overview
This lecture explains how our brain processes visual information from both eyes, specifically how light from different parts of the visual field is transmitted to the appropriate sides of the brain.
Visual Pathways and the Visual Field
- Each eye receives light from both the left and right visual fields.
- The nasal side of each eye is closest to the nose; the temporal side is closest to the temples.
- Light from the left visual field hits the nasal retina of the left eye and the temporal retina of the right eye.
- Light from the right visual field hits the nasal retina of the right eye and the temporal retina of the left eye.
The Optic Nerve and Optic Chiasm
- The optic nerve connects the back of each eyeball to the brain.
- Both optic nerves meet and partially cross at the optic chiasm.
- Axons from the nasal sides of both retinas cross over at the optic chiasm to the opposite side of the brain.
- Axons from the temporal sides do not cross at the optic chiasm; they continue on the same side.
Brain Processing of Visual Information
- Information from the right visual field is sent to the left side of the brain.
- Information from the left visual field is sent to the right side of the brain.
- This crossing ensures that each hemisphere processes visual data from the opposite visual field, consistent with other body systems.
Key Terms & Definitions
- Nasal Side — the side of the retina closest to the nose.
- Temporal Side — the side of the retina closest to the temples.
- Optic Nerve — the nerve carrying visual information from the retina to the brain.
- Optic Chiasm — the point where the optic nerves from each eye partially cross.
Action Items / Next Steps
- Review diagrams of the visual pathway, especially the optic chiasm.
- Be prepared to label the optic chiasm, optic nerves, nasal and temporal sides in a diagram.