Vision, Optic Tract, Optic Tract Injuries and Implications

corrugator supercilii

muscle of the eye

depresses and pulls the eyebrow medially

corrugator supercilii expresses

expresses concern or confusion

orbicularis oculi

muscle of the eyes

involuntarily closes the eyelid such as when blinking or sleeping (palpebral fibers)

forcefully closes the eye such as when squinting or expressing pain (orbital fibers)

orbicularis oculi innervated by

CN7 (facial nerve)

extraocular muscles

7 muscles that act to move the eye and one muscle that elevates the eyelid (levator palpebrae)

levator palpebrae

elevates the eyelid

fast-twitch extra ocular muscles provide

linear and rotary motion of the eyeball, allowing for scanning the visual field

optokinetic reflex

stabilizes the visual field as the head moves through the surrounding environment

______ _______ of the eye muscles is necessary for coordinated, simultaneous movements, producing complementary images from the right and left visual fields

symmetrical cooperation

unilateral weakness or paralysis can lead to

diplopia

diplopia

double-vision; limits the ability of the eyes to scan the visual field

ptosis

refers to drooping of the eyelid and may result from weakness of the levator palpebrae

a complete lesion of the optic nerve anterior to the optic chiasm leads to

complete ipsilateral field loss

lesions at the optic chiasm cause

bitemporal deficits, or loss of peripheral vision on both sides

lesions posterior to the optic chiasm or in the occipital lobe of the brain contribute to

partial or full homonymous hemianopsia

homonymous hemianopsia

loss of vision on the same side of each visual field

individuals with visual field loss may benefit from

cueing to scan the environment or from specialized prism glasses to “fill in” the missing visual field

sclera and cornea make up the

outer shell

sclera

thick fibrous capsule around the eye, helps give shapecon

cornea

right at the front of the eye, attaches to the sclera, lets light in

anterior cavity has both an

anterior and posterior chamber

anterior chamber of anterior cavity is filled with

aqueous humor

anterior chamber of anterior cavity is between

iris and cornea

aqueous humor

watery fluid substance that provides pressure so that the eye doesn’t collapse in on itself

posterior chamber of anterior cavity is between

lens and iris

posterior chamber of anterior cavity is filled with

aqueous humor

lens

refracts light onto the retina at fovea centralis

ciliary body and suspensory ligaments help the lens to

change shape to refract light

posterior cavity is where?

behind the lens

posterior cavity is filled with

vitreous humor

vitreous humor

gelatinous, helps keep shape in the posterior cavity

choroid

vascular layer

extrinsic muscles of the eye (6 + 1)

4 rectus muscles, 2 oblique muscles +1

superior rectus

inferior rectus

medial rectus

lateral rectus

superior oblique

inferior oblique

levator palpebrae (+1)

superior rectus

pulls eye up

inferior rectus

pulls eye down

medial rectus

pulls eye medially

lateral rectus

pulls eye laterally

superior oblique

pulls eye down and out

inferior oblique

pulls eye up and out

optic nerve innervates the

retina

facial nerve innervates

orbicularis oculli

Cranial nerve 3 innervates

superior rectus muscle, medial rectus muscle, inferior oblique, inferior rectus muscle

cranial nerve 4 innervates

superior oblique muscle

CN6 innervates

lateral rectus muscle

all muscles of eye attach at

common tendinous ring

true or false: axis of forward gaze and axis of orbit and muscles are aligned.

false

what muscles are involved?

right superior rectus

left inferior oblique

right superior rectus

left superior rectus

right inferior oblique

left superior rectus

right lateral rectus

left medial rectus

right medial rectus

left lateral rectus

right inferior rectus

left superior oblique

right and left inferior rectus

right superior oblique

left inferior rectus

iris has 2 muslces

outer radial muscle, inner circular muscle

parasympathetic (r&d) stimulates the circular muscle resulting in

pupillary constriction from sphincter pupillae

sympathetic (fof) stimulates the radial muscle causing

pupillary dilation from dilator pupillae

the optical apparatus mechanistically collects and focuses light at ___:____ on the retina

280:1

optic disc

where the optic nerve enters the eye and collects info from the retina; blindspot - there are no rods or cones

central 5 degress (radial) contains ____% of all RGCs (retinal ganglion cells)

12

central 10 degrees contains __% of RGCs

34

central 20 degrees contains __% of RGS

54

_____ input is a primary component of ADLs and IADLs

visual

two pathways from primary visual cortex (PVC)

dorsal stream and ventral stream

dorsal stream

the “where” pathway (to parietal lobe)

location, movement, spatial relations

ventral stream

the “what” pathway (to temporal lobe)

color, texture, shape, size, detail

memory

pre-chiasmatic lesions affect

one eye only

optical apparatus lesion

damage to lens, cornea, or sclera

post/retro-chiasmatic lesions usually affect

both eyes and require extensive screening

what is it? what does it result in?

distal optic nerve lesion

results in monocular blindness

distal optic nerve lesion; progressive lesion of the optic nerve typically causes

tunnel vision

distal optic nerve lesion; acute lesion or untreated progression typically causes

unilateral blindness (anopia)

distal optic nerve lesion; partial acute lesion can cause

unilateral scotoma/anopia

proximal optic nerve lesion

scotoma

partial loss of vision in a visual field

proximal optic nerve lesion

junctional scotoma

what is it? what does it result in?

midsagittal optic chiasm lesion

bitemporal hemianopia, ipsilateral fibers remain intact but decussation fibers are lesioned

what is it? what does it result in?

optic tract lesion

complete right or left visual field deficit, right homonymous hemianopia

what is it? what does it result in"?

temporal lope optic radiations lesion

right homonymous superior hemianopic defect (“pie in the sky”)

what is it? what does it result in?

parietal lobe optic radiations lesion

right homonymous inferior hemianopic defect (“pizza on the floor”)

what is it? what does it result in?

occipital lobe optic radiations lesion

“pizza on the floor” anopia, “pie in the sky” anopia, put together: homonymous hemianopia

what is it? what does it result in?

occipital lobe optic radiations lesion

right homonymous scotomas

CVA lesions: Middle Cerebral Artery supplies

lateral surfaces of cerebral cortex (frontal, parietal, and temporal lobes)

CVA lesions: Middle Cerebral Artery complications:

contralateral hemianopsia, visuospatial deficits

CVA lesions: anterior cerebral artery supplies

medial aspects of cerebral cortex (frontal and parietal lobes)

CVA lesions: anterior cerebral artery complication:

homonymous hemianopsia

CVA lesions: posterior cerebral artery supplies

occipital lobe, inferior aspects of temporal lobe, parts of brainstem

CVA lesions: posterior cerebral artery complications

CN3 paralysis, homonymous hemianopsia, visual agnosia

CVA lesions: vertebral basilar artery supplies

medulla, pons, CNs, cerebellum

CVA lesions: vertebral/basilar artery complications

horner’s syndrome (pupil constriction, ptosis, anhidrosis), nystagmus, CN paralyses, paralysis of conjugate gaze (eyes don’t move together)

aphasia

loss of ability to understand or express speech

Broca’s Area

frontal lobe

motor speech

• language production

• expressive aphasia (Broca’s aphasia) — cannot express what they are trying to say

  • word salad

Wernicke’s Area

temporal lobe

associative auditory

• language comprehension

• receptive aphasia — can’t understand what someone is saying

Wernicke’s and Broca’s area would be impacted by CVA lesions to

middle cerebral artery and some of anterior cerebral artery and PCA

pre-chiasmatic lesions affect

one eye only

post-/retro-chiasmatic lesions usually affect

both eyes

acute lesion or untreated progression typically causes

unilateral blindness (anopia)

partial acute lesions can cause

unilateral scotoma/anopia