Visual System Part II And III Flashcards
What are the first order neurons of the optic pathway
Ganglion cells that travel in the optic nerve into the optic chiasm
What do axons coming from the lateral retina do at the optic chiasm
Do not decussate, they enter the ipsilateral optic tract
What do the axons that come from the medial retina do at the level of the chiasm
Decussate and enters the contralteral optic tract
Where do fibers from each optic tract terminate
In the lateral geniculate nucleus
What are the second order neurons in the optic pathways
Geniculate fibers
Where do the geniculate fibers travel
Through the internal capsule and corona radiata to the primary visual cortex in the banks of the calcarine sulcus
What is the extra geniculate pathways
Sensory fibers for pupil/EOM movements
Where do the extra geniculate fibers enter
They bypass the LGN and enter the pretectal area and the superior colliculus
What is the pretectal area important for
Pupillary light reflex
What is the superior colliculus and the pretectal area involved with
Directing eyes toward visual stimuli
Is the extra geniculate pathway involved with vision
No
Fibers arising from the lateral geniculate nucleus curve around the lateral wall of the lateral ventricular as the _________
Optic radiation
Where do the optic radiations terminate
In the cortex adjacent to the calcarine sulcus
What part of the visual field does the upper retina represent
Lower
Where does the upper retina projector in the calcarine sulcus
Above the calcarine sulcus
What part of the VF does the lower retina represent
Upper VF
What part of the calcarine sulcus does the lower retina project to
Below the calcarine sulcus
How do projections from the upper retina course in the optic radiations
Upwards in parietal lobe, around lateral ventricle to visual cortex above calcarine
How do the lower retina optic radiations course back
Downwards through temporal lobe towards calcarine sulcus
Where do the macular fibers project
In a broad region, some go with the superior optic radiations, some with the inferior optic radiations
Lesions affecting the optic radiation and the macula
Often cause visual loss in one quadrant of the vision field with macular sparing
Superior retina projects
To the cortex above the calcarine sulcus
Inferior retina projects to the
Cortex below the calcarine sulcus
Where is the macula represented
More posteriorly and peripheral fields than anteriorly. Represents a large area of the primary visual cortex
Representation of the macula compared to its size
Disproportionately large
What is the blood supply of the optic radiations
MCA
What is the blood supply for the superior branch of the optic radiation
Superior branch of MCA
What is the blood supply of the inferior optic radiations
Inferior branch of the MCA
What is the blood supply to the visual cortex
PCA
How are visual named
According to the VF loss and NOT ACCORDING TO THE AREA OF THE RETINA OR THE OPTIC PATHWAY THAT IS NONFUNCTIONAL
Loss of the whole VF in one or both eyes
Blindness
Loss of half of a VF
Hemianopia
Loss of one quarter of a VF
Quadrantanopia
Same field loss in both eyes
Homonymous
Opposite field loss in both eyes
Heteronimous
What is often used instead of heteronimous lateral hemianopia?
Bitemporal hemianopia
What is often used instead of left or right homonymous hemianopia
Left or right hemianopia
Is the lesion is before the chiasm
One eye is affected
If the lesion is after the chiasm
Both eyes are affected
Optic nerve damage
Ipsilateral blindness (right ON damage, right blindness)
Damage to the optic chiasm in the middle
Bitemporal hemianopia
VF loss in each eye temporally
Damage to the right optic chiasm from the side more temporally
Left hemianopia in the right eye
Damage to the right optic tract
Left homonymous hemianopia
Same as if we lose the geniculate nucleus
What is a common causes of damage to the optic chiasm
Pituitary tumor
What is a common thing to damage the optic nerve
Embolism
Ischemia or infarct in the temporal lobe (MCA) at the Meyers loop on the inferior optic radiation
Left superior quadrantanopia
Pie in the sky
Ischemia or infarct in the temporal and occipital lobe or the visual cortex (MCA or PCA, affects both loops)
Right past the Meyers loop that affects both inferior and superior optic radiations
Left homonymous hemianopia
Ischemia or infarct in the parietal or occipital lobe (MCA or PCA, affects superior optic radiation) kinda close to the visual cortex
Left inferior quadrantanopia
Ischemia or infarct in the temporal or occipital lobe (MCA or PCA, affects inferior loops) kinda close to the visual cortex
Left superior quadrantanopia
Quadrantanopia with macular sparing
- ischemia or infarct affecting superior or inferior optic radiation
- macula is spared because it is presented in BOTH parts of the optic radiation
What radiation would need to be affected to get lower quadrantanopia
Superior
What radatiation would be affected if you have upper quadrantanopia
Inferior
Why do we get macular sparing if there is ischemia or infarct affecting occipital lobe that is supplied by the PCA?
Because the region of the occipital lobe where the macula is represented is ‘saved’ by collaterals coming from the MCA territory
What do we “see” with
Our brains
How does the brain perceive things
We detect motion, light and dark, and color and the abstracted properties are somehow reassembled into a unified perception.
Our visual system can recognize objects independent of what
Angle or view, distance, and illumination
Most input to primary visual cortex arrives at what cortical layer
4
What is cortical layer 4 subdivided into
4A, 4B, 4Ca, 4b
What cortical layer in 4 contains numerous myelinated axon collateral resulting in the pale- appearing stria of gennari that is visible with the naked eye?
Layer 4B
Because of the distinctive stria from cortex layer 4B, what is the primary visual cortex also referred to as
Striate cortex
Visual association cortex
From the primary visual cortex, neurons project to this area and other regions of the parietal-occipital and occipitotemporal cortex.
What are the two main streams of higher order visual processing that are demonstrated in animals and humans
- dorsal pathways that project to the parietal-occipital association cortex (Where?)
- ventral pathways that project to the occipitotemporal association cortex (What?)
What do the dorsal pathways of the visual association cortex do
Anywhere the question ‘where?’ by analyzing motion and spatial relationships between objects as well as between the body and visual stimuli
What does the ventral pathway of the visual association cortex do
Answers the question “what?” by analyzing form, with specific regions identifying colors, faces, letters, and other visual stimuli
Where is the separation of the dorsal and ventral pathways of the visual association cortex?
At the level of the retina
Channels for analyzing motion, form, and color
All sent through different parallel channels that go to different layers of the primary visual cortex
What is the condition where patients are unable to recognize people by looking at their faces
Prosopagnosia
What type of lesion is responsible for prospagnosia
Bilateral inferior occipitotemporal cortex, also known as the fusiform gyrus
Which hemisphere is mroe important for face recognition?
Some say the right one is, but in most reported cases, lesions are bilateral
People with prosopagnosia cannot recognize people by their face, but they can identify people by what
Their clothes, voices, or other cues
Awareness of the left hemisphere
Is aware of the right part of the world
Right hemisphere awareness
Aware of both with only slight dominance to the left
The VFs in someone with hemineglect syndrome
Intact
What does the damage affect in hemineglect syndrome
Right hemisphere
What is there an inability of in he I neglect syndrome
To pay attention to or notice stimuli from one half of the VF
Where does the loss occur in someone with meineglect syndrome
Occurs on the left side of the VF as the result of right parietal damage
What are some weird things that people with me I neglect syndrome do
Perceive only the right half of an object, if asked to copy an image, they will only draw the right half. They will eat food from only half of their plate
Results in decreases or absent vision in an eye that otherwise is normal
Amblyopia
Whenever the eye does not receive visual signals from an eye for a long period of time there is a risk of
Amblyopia
Where is the cause of amblyopia
Within the brain
What increases the chance of successful treatment in children with amblyopia
Detecting strabismus in early childhood
Most common cause of amblyopia
Strabismic amblyopia
What are the types of amblyopia
Strabismic
Refractive (differing refractive error)
Deprivation (congenital cataract)
What is a symptom give away for someone with an embolism
Sudden visual loss in one eye
What is a symptom give away for RD
A veil falling or black curtain
What is a symptom giveaway for someone floaters
Dust particle, lint, moving black spots
What is a symptom give away for someone with acute angle closure glaucoma
Pain and redness
What is a symptom giveaway for viral conjunctivitis
Redness with WATERY discharge
What is a symptom give away for bacterial conjunctivitis
Redness with PURULENT discharge
