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Questions and Answers
Damage to the upper and lower bank of the calcarine fissure would most likely result in which of the following visual impairments?
Damage to the upper and lower bank of the calcarine fissure would most likely result in which of the following visual impairments?
What visual condition is characterized by partial loss of vision in the same half of both eyes with the center macula spared?
What visual condition is characterized by partial loss of vision in the same half of both eyes with the center macula spared?
Which artery affects the area of the occipital lobe that can lead to contralateral homonymous hemianopia?
Which artery affects the area of the occipital lobe that can lead to contralateral homonymous hemianopia?
What is the main characteristic of macular sparing in the context of visual impairment?
What is the main characteristic of macular sparing in the context of visual impairment?
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Scintillation is best described as:
Scintillation is best described as:
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What is the meaning of a scotoma in relation to vision?
What is the meaning of a scotoma in relation to vision?
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What does macular degeneration primarily affect?
What does macular degeneration primarily affect?
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What type of impairment occurs when a patient can only see through peripheral vision but not through central retina?
What type of impairment occurs when a patient can only see through peripheral vision but not through central retina?
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Which area is most affected by lesions in the occipital cortex/primary visual cortex?
Which area is most affected by lesions in the occipital cortex/primary visual cortex?
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Study Notes
The Posterior Pole of the Eyeball
- The posterior pole of the eyeball is connected to the optic nerve (CN II), which transmits information from the retina to the brain.
- The optic nerve conveys visual information from the retina to the brain for processing.
Structure of the Retina
- The retina has two layers: Retinal Pigment Epithelium (RPE) and Neural Retina.
- The RPE is the deepest layer, firmly attached to the choroid, and is responsible for nourishment.
- The Neural Retina is important for vision, conveying visual messages, and derives from the diencephalon.
Retinal Layers
- The retina has 10 histological layers in the vitreous humor.
- There are 3 functional layers: Cones and Rods, Bipolar Cells, and Ganglion Cells.
Retinal Cells
- Ganglion Cells: 2nd order neurons in the visual pathway, multipolar cells that synapse with bipolar and amacrine cells, and send output to the Lateral Geniculate Nucleus (LGN) of the thalamus.
- Amacrine Cells: Help with processing/modulating information, synapse with dendrites of ganglion cells and bipolar cells, and have an indirect connection between ganglion and bipolar cells.
- Bipolar Cells: 1st order neurons in the visual pathway, collect information from photoreceptors and give information to ganglion cells.
- Horizontal Cells: Help with processing/modulating information, located around apices of rods and cones, and synapse with rods and cones.
- Cone & Rod (Receptors/Transducers): Respond to electrical impulses and action potentials, located in the deepest layer of the neural retina, and do not come in contact with light first.
Visual Pathway
- Optic Tract: Passes through the pulvinar nucleus and synapses with the LGN.
- Lateral Geniculate Nucleus (LGN): Part of the thalamus, relay station, 3rd order sensory neurons, and synapse happens here, projecting fibers into the visual field.
- Optic Radiation: Fibers from LGN to visual cortex, carrying visual information from the contralateral visual field.
- Lower (Inferior) Optic Radiation: Carries information from the superior visual field and located on the lateral side of optic radiations.
- Upper (Superior) Optic Radiation: Carries information from the inferior visual field and located on the medial side of optic radiation.
Blood Supply
- Optic Radiation: Receives blood supply from the middle cerebral artery and posterior cerebral artery.
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Description
Test your knowledge on the visual pathway and the role of the thalamus in processing visual information. Learn about how fibers travel from the optic tract to the Lateral Geniculate Nucleus (LGN) and the representation of the visual field.
