OT 6000 Test 5- Ch 21

Question 1

Cranial Nerves that contribute to sight

Answer 1

• CN 2: vision- brings AP’s from light information on eyes to the back of the brain
• CN 3: eye movement and control of pupil and lens (controls what we see)
• CN 4: eye movement (down and in)
• CN 6: eye movement (abduction)
• ->3,4, and 6 point eyes where you want to look

Question 2

Temporal vs Nasal Retina

Answer 2

• Temporal retina: portion of retina close to temporalis

- Nasal retina: portion of retina close to the nasal bone

Question 3

Temporal visual field vs Nasal visual field

Answer 3

• Temporal visual field: visual field for one eye that shows out to the side vision
• Nasal visual field: visual field for one eye that shows vision in front of nose and distally past that

Question 4

Path of vision from eye to cortex

Answer 4

Optic nerve> optic chiasm (where nasal retina passes over to other side)> optic tract> lateral geniculate nucleus> thalamus> visual cortex

Question 5

Optic Chiasm

Answer 5

Where axons from the nasal retina cross over midline; pulls all the information from one side of visual space into opposire occipital lobe.

Question 6

Dorsal stream vs ventral stream

Answer 6

• Dorsal stream: Action stream- comes into the parietal to make sense and ends in the motor planning area
• ->uses what I see to guide motor plan to move
• Ventral stream: perception stream- gives meaning and a name to what you see.
• > comes from occipital lobe down to inferior temporal lobe (stores memories)

Question 7

Condition leading to blindness of one eye

Answer 7

• One optic nerve is cut
• will lead to loss of depth perception
• eyes are capable of seeing 180 degrees, but nose, eyebrows and chin will cut visual field short on side of vision loss

Question 8

Bitemporal hemianopsia

Answer 8

• Cut on the optic chiasm, which will severe the nasal retina from both sides (since they cross over at this area)
• leads to loss in temporal visual fields on both sides (tunnel vision)
• common in CVA’s

Question 9

Homonymous hemianopsia

Answer 9

• Cut on one optic tract: both eyes lose half of vision in the SAME SIDE
• All light information from one side of vision is cut

Question 10

Quadrantanopsia

Answer 10

• cut of one optic radiation

- One forth of vision loss on SAME SIDE of both eyes

Question 11

Cortical blindness

Answer 11

• Blindness due to damage in visual cortex of brain
• may see light and dark, and even resolve some shapes, but will not be able to resolve finer details to give meaning to what is seen

Question 12

Pupillary light reflex

Answer 12

Pupil constricting when light is shine in eyes

• Direct: eye that light is shining in constricts
• Consensual: other eye has constriction as well, without light being shined into it
• ->CN II provides stimulus, CN III adjusts pupil via parasympathetic

Question 13

CN 3, 4, and 6 control of eye movement

Answer 13

4. Down and in
5. Straight abduction
6. Everything else
   - ->wiring in brain connects these CN’s together on both sides. This is why abduction of one eye is accompanied by adduction of the other eye

Question 14

CN III Occulomotor nerve- palsy

Answer 14

Would lead to one eye being overly lateral when looking straight ahead

• CN IV will win and pull eye into abduction since III is not tugging eye into adduction
• affected eye will also be dilated due to parasympathetic not functioning properly

Question 15

CN IV- Trochlear- palsy

Answer 15

Pt will be unable to look down and in on affected side

• CN IV not pulling eye down and in; CN III can help adduct eye, but eye will be looking up instead of in with loss of IV.
• Pt with this palsy will tilt head to balance

Question 16

CN VI- Abducens- palsy

Answer 16

Affected eye will not be able to abduct out to look in lateral vision

Question 17

Medial Longitudinal Fasciculus damage

Answer 17

Will look like CN III damage, but pupils will not dialate because parasympathetic not affected
–This is because MLF is where all CN’s of eye movement are connected to make movements work together

Question 18

Gaze stabilization

Answer 18

Keep eyes focused on an object of interest while the head is moving
-VOR: Vestibulo-Occular- Reflex

Question 19

Direction of gaze

Answer 19

Move the eyes to focus on an object of interest

-aka: optokinetic reflex, aka: smooth pursuit

Question 20

VOR

Answer 20

• Vestibulo-Occular-Reflex: gaze stabilization reflex
• inner ear plays a big role in this
• Can suppress VOR when needed (ex: following finger movement while head moves)

Question 21

Optokinetic Reflex

Answer 21

• Ability to stay focused on object of interest during slow head movement
• Optokinetic nystagmus: occurs when eyes are following something that is moving (this is normal because head IS MOVING)

Question 22

Saccades

Answer 22

Voluntarily looking from one object to the next

-Can be reflexive: superior colliculi makes eye jump to something in peripheral vision

Question 23

Smooth pursuit

Answer 23

Optokinetic reflex working to slowly move eye along path (happens when reading)

Question 24

Vergence (convergence)

Answer 24

Crossed eyes movement- keeping object in focus as it gets closer and closer to face

Question 25

Motion sickness

Answer 25

Usually a conflict between different sensory systems: some say you are moving, some say you are NOT moving. Vestibular nuclei can’t decide and freaks out to make you stop what you are doing