Orbit, Eye, & Vision Part 3 - Herring Flashcards
entire area of space that a person can see at a given moment
visual field
the specific area on the
retina where light from
that part of the visual field is projected
essentially, where part of the visual field projects onto the actual retina
retinal field
using 2 eyes at the same time to create a single image of the world
binocular vision
2 visual fields for binocular vision, explain them and what the the area of overlap assists with
1 for the left eye
1 for the right eye
Area of overlap in the middle to assist with depth perception
Visual field of each eye is divided into ________ and ________ regions
temporal (lateral) ; nasal (medial)
Both temporal and nasal visual fields are further divided into _____ and ______ visual fields
superior ; inferior
Ultimately ___ quadrants in each visual field
4
Retina of each eye is also divided:
Temporal retina =
lateral retina
Retina of each eye is also divided:
Nasal retina =
medial retina
After passing through the lens, light from each portion of the visual field projects to the _______ side of the retina
opposite
Visual world projects onto retina with a specific _______
orientation
At the lens the image from the visual field/outside world is ______ and ________
inverted ; left/right reversed
View of the right side of the “world” (right visual fields) represented on the :
Nasal retina of the ____ eye
Temporal retina of the ____ eye
right
left
View of the left side of the “world” (left visual fields) represented on the :
Nasal retina of the ____ eye
Temporal retina of the ____ eye
left ; right
Each optic nerve (CN II) then carries a “full” representation of the ____ & ____ sides of the world
right and left
each optic nerve (CN II) carries the entire visual field for the _____ eye
ipsilateral
Left optic nerve = carrying the left (temporal) visual field on _____ retina and right (nasal) visual field on ______ retina
nasal ; temporal
Lesion of the optic nerve (CN II) = blindness from the ____ eye
SAME
Monocular vision loss!!
(loss of right & left sides of the visual fields from the ipsilateral retina)
Optic Chiasm - “Peripheral vision” fibers / temporal visual fields ______
Cross / Decussate
Optic Chiasm –> PERIPHERAL VISION - from the right optic nerve =
fibers from the nasal retina (carrying the view of the temporal visual field / “right side of the world”) ______
CROSS
Optic Chiasm –> PERIPHERAL VISION - from the left optic nerve =
fibers from the nasal retina (carrying the view of the temporal visual field / “left side of the world”) ______
CROSS
Optic Chiasm –> CENTRAL VISION - from the right optic nerve =
fibers from the temporal retina (carrying the view of the nasal visual field / “right side of the world”) do not _____
CROSS
Optic Chiasm - “CENTRAL VISION” fibers do not ____
cross
Optic Chiasm –> CENTRAL VISION - from the left optic nerve =
fibers from the temporal retina (carrying the view of the nasal visual field / “left side of the world”) do not _____
CROSS
Lesion at the optic chiasm that only affects the middle (crossing / decussating) fibers =
tunnel vision (patient loses peripheral vision / temporal visual fields)
BITEMPORAL HEMIANOPIA
Lesion at the optic chiasm that affects all of the optic chiasm =
blindness from both eyes
The optic tract extends from the optic chiasm to the ______ on each side
thalamus
Each optic tract carries the visual field of the ______ side
opposite
Optic Tract - Right optic tract carries _____ side of the “world” (visual field)
left
Optic Tract - Left optic tract carries ___ side of the “world” (visual field)
right
Lesion at the optic tract
Opposite side goes dark
(Contralateral homonymous hemianopia)
(a visual defect that causes loss of vision in the same half of the visual field in both eyes)
Right optic tract lesion = loss of the ____ side of the visual field from ____ eyes
left ; both
Left optic tract lesion = loss of the _____ side of the visual field from _____ eyes
right ; both
Pathway of Vision
Most fibers of each of the optic tracts then project to ________ in their ipsilateral lateral geniculate nucleus (LGN) of the ______
2nd order cell bodies
thalamus
Pathway of Vision
Each lateral geniculate nucleus projects to its ___________
ipsilateral occipital cortex (primary visual cortex)
Pathway of Vision
Between lateral geniculate nucleus & the occipital cortex, the fibers carrying the upper and lower visual fields ______
separate
Lesions between the lateral geniculate nucleus & the occipital cortex can result in losing a ________ of the visual field from ______ eyes
quadrant ; both
Leading cause of severe vision loss in those >50 years (~10 million people in US)
Macular Degeneration
Vision loss in the center of visual field
Macular Degeneration
Damage to the cone-dense macular region of retina (trouble discerning colors)
Blurry central vision that can progress to blind spot(s) in the central vision
Peripheral vision remains
Macular Degeneration
Progressive accumulation of protein deposits in the macula (~85% of cases)
Deposits may further dry and thin macula which increases symptoms
Dry Macula Degeneration
abnormal leakage of blood vessels deep to the macula causing fluid to build up & scar the macula
Wet Macular Degeneration
Complication from diabetes affecting the blood vessels of retina
Diabetic Retinopathy
Blood vessels weaken, bulge, or leak into retina due to high blood sugar levels
Causes retina to swell, potential hemorrhages
Diabetic Retinopathy
Early: changes in near or distant vision, blurry vision
Later stages: dark eye floaters caused by leakage of blood or scarring of retina by the leaky vessels. New blood vessels grow on the retina (fragile & bleed into the vitreous body). Increased likelihood of retinal detachment
Diabetic Retinopathy
Pupillary Light Reflex
A smaller subset of fibers from the optic tracts project to their _____ pretectal nucleus
ipsilateral
Pupillary Light Reflex
Each pretectal nucleus projects _______ to the right & left Edinger-Westphal nucleus
bilaterally
Pupillary Light Reflex
Each Edinger-Westphal nucleus (preganglionic parasympathetic cell bodies) sends its axons peripherally as part of their
ipsilateral CN III (oculomotor nerve)
Pupillary Light Reflex
The preganglinic parasympathetic fibers of each CN III synapse on their IPSILATERAL __________
ciliary ganglion (postGPS cell bodies)
Pupillary Light Reflex
Postganglionic parasympathetic fibers “hitch-a-ride” on their ipsilateral _____________ nerves to pierce the ______ to the ________ and _________
short ciliary nerves ; eyeball ; constrictor pupillae & ciliary muscle
Lesion to the optic nerve:
Light shined in the ipsilateral pupil
Neither pupil constricts
Brain does not know there is light projecting onto the retina
Lesion to the optic nerve:
Light shined in the contralateral pupil
Both pupils dilate
Brain perceives there is light through the intact pupil
No damage to parasympathetic (motor) pathways
Lesion to the Edinger-Westphal nucleus, PreGPS fibers of CN III, ciliary ganglion, or postganglionic parasympathetic fibers (lesion to the motor component of the reflex):
Ipsilateral pupil size does ____ change (does not constrict) when a light is projected into either eye
not
No motor signal reaches the constrictor pupillae to tell it to constrict
Lesion to the Edinger-Westphal nucleus, PreGPS fibers of CN III, ciliary ganglion, or postganglionic parasympathetic fibers (lesion to the motor component of the reflex):
Contralateral pupil _____ when a light is projected into either eye
constricts
Motor pathway intact so signal reaches the constrictor pupillae as expected
Right optic tract - fibers from the temporal retina of the _____ eye & the nasal retina of the _____ eye
right ; left
Left optic tract - fibers from the nasal retina of the _____ eye & the temporal retina of the _____ eye
right ; left
