Visual Tracts (Dennis) Flashcards
What are the tunics/layers of the eye
Fibrous Layer
Vascular Layer
Retina
What layer of the eye touches the external layer
What does it consists of?
Fibrous layer
The sclera and cornea
What layer of the eye consists of the choroid, ciliary body and iris
Vascular layer
What is the inner sensory layer of the eye that gives rise to the optic nerve
Retina
What is the sclera
What is the tissue type
Fibrous, external layer of the eyeball that protects internal structures and provides sites for muscle insertion.
Dense regular CT, with flat bundles of type I collagen and microvascular near the outer surface
List the layers of the cornea
- Corneal epithelium
- Anterior limiting membrane (Bowman membrane)
- Stroma comprised of keratocytes
- Posterior limiting membrane (Descemet’s membrane)
- Inner endothelium
What is the transitional area where the transparent cornea merges with the opaque sclera and encircles the entirety of the cornea
Limbus
What are the layers of the retina and what are the cell types attributed to them
- Outer Pigmented layer: Simple cuboidal epithelium
- Inner Neural layer: Thick and stratified with various neurons and photoreceptors
Neural components of the retina extend anteriorly to where
Ora Serrata
What are the functions of the pigmented epithelium (PE)
- Absorbs scattered light
- Forms part of the blood-retina-barrier
- Isomerizes all-trans-retinal to 11-cis-retinal and transfers back to photoreceptors
- Phagocytosis & degeneration of waste from photoreceptors
- Removes free radicals & secretes ATP, polypeptide growth factors & immunomodulatory factors
What are the layers of the Neural Retina from superficial to deep?
- Inner limiting membrane (ILM)
- Optic nerve fiber layer (NFL)
- Ganglionic layer (GL)
- Inner plexiform layer (IPL)
- Inner nuclear layer (INL)
- Outer plexiform layer (OPL)
- Outer nuclear layer (ONL)
- Outer limiting layer (OLL)
- Photoreceptors: Rod & cone layer (RCL)
- Pigmented layer (PL) - not actually part of NL
Mnemonic: In Our God IIs Ooour Pure Purpose
What are the function of the inner and outer segments of rods
Inner segment: contains glycogen, mitochondria and polyribosomes for the cell’s biosynthetic activity
Outer segment: Contacts the pigmented epithelium and contains flattened membranous discs that contain rhodopsin
Iodopsin
The visual pigment contained by cones
What is the Fovea Centralis
Area in retina with the highest concentration of cones, making it the area where visual acuity is sharpest. Absence of vessels, cell bodies and axons of ganglionic and inner nuclear layer
What is the Macula Lutea
Surrounds the fovea and protects cones. Has antioxidant properties and short wave UV filter.
Characteristics of the optic disc
Located at head of optic nerve where ganglion axons from all of the retina converge and dive. Lacks photoreceptors so it’s a blind spot
What is the optic nerve
Axons of retinal ganglion cells that become myelinated as they pass through the sclera and penetrate the chroroid as it travels to the brain.
What is the name for the areas that a person is able to see when both eyes are fixed in one position
Visual fields
Binocular zone
The broad central region seen by both eyes
What is the area seen only by one eye (R/L)
Monocular zone
Retinal field
Location on the retina that an object in the visual field is projected
What is the retinal field divided into
Retinal hemifields: nasal & temporal
quadrants: upper and lower
The right half of the visual field forms an image upon what part of the retina?
Temporal (left) half of the left retina
Nasal (left) half of the right retina
The left half of the visual field forms an image upon what part of the retina?
Nasal (right) half of the left retina
Temporal (right) half of the right retina
In what direction do the nasal half of each retina move in the optic chiasm
Contralateral optic tract
In what direction do the temporal halves of each retina move
Ipsilateral optic tract
What fibers make up the optic tract
Fibers from temporal retina (ipsilateral eye) + fibers from nasal retina (contralateral eye)
Where do fibers of the optic tract terminate
lateral geniculate nucleus (LGN)
What are out going fibers from the lateral geniculate nucleus called?
Optic radiations
What visual information is received by the right lateral geniculate
Left visual field images = Left nasal + Right temporal –> Right LGN
What visual information is received by the left lateral geniculate
Right visual field images = Left temporal + right nasal –> Left LGN
Where do optic radiation relay their information
Primary visual cortex
Where is the primary visual cortex located
upper & lower banks of the calcarine sulcus
Fibers in the upper retina contain information about what visual field
Lower visual field
Fibers in the lower retina contain information about what visual field
Upper visual field
What is the route of upper visual field information to the brain?
Upper visual field stimuli –> lower retina —> optic nerve –> optic tract —> lateral geniculate –> Meyer loop —> lingual gyrus (inferior bank of sulcus)
What is the route of lower visual field information to the brain
lower visual field stimuli –> upper retina —> optic nerve –> optic tract —> lateral geniculate –> cuneus (superios bank of sulcus)
What is the parieto-occipito-temporal area
The visual association cortex that helps interpret location, motion, form and color
What structure is important in directing eye movement
Superior colliculus
What structure is important in the pupillary light reflex
Pretectal/pretectum area
Hemianopia/Hemianopsia
Blindness in one-half of the visual field
Quadrantanopia
Blindness of a quadrant of the visual field
Homonymous visual fields
Conditions in visual field losses are similar in both eyes
Heteronymous visual fields
Conditions in which the two eyes have non-overlapping field losses
Macular sparing
Visual field loss that preserves vision in the center of the visual field
Damage anterior to the chiasm affects what
Only the ipsilateral eye
Damage at the chiasm causes what kind of deficits
heteronymous deficits
Damage behind the chiasm causes what kind of deficit
Homonymous deficits
What is associative visual agnosia
Infraction of the left occipital lobe and posterior callosum, typically due to PCA damage, which leads to a disconnect between the language area and the visual association cortex. Patient may also be unable to read (alexic) and writing ability may be affected (agraphia)
Patient cannot name or describe an object in the visual field, but he can recognize and demonstrate its use
