Visual control and reflexes

Question 1

Q: Definition of Diplopia?

Answer 1

A: Perception of two images of the same object

Question 2

Q: Definition of Strabismus?

Answer 2

A: Misalignment of the position of the two eyes

Question 3

Q: Type of strabismus where one eye is higher than the other?

Answer 3

A: Hypertropia

Question 4

Q: Type of strabismus characterized by an outward, horizontal misalignment?

Answer 4

A: Exotropia

Question 5

Q: Type of strabismus characterized by an inward, horizontal misalignment?

Answer 5

A: Esotropia

Question 6

Q: What is Amblyopia (Lazy Eye)?

Answer 6

A: Poor development of neural pathways to an affected eye, usually due to strabismus in childhood

Question 7

Q: Two main types of eye movements?

Answer 7

A: Conjugate movements (eyes move in the same direction) and Vergence (eyes move in opposite directions)

Question 8

Q: Definition of Convergence (Vergence)?

Answer 8

A: Both eyes deviate nasally (inward) to focus on a near object.

Question 9

Q: The 3 components of the Accommodation Reflex (for near objects)?

Answer 9

A: 1. Vergence (Medial rectus mm.), 2. Lens becomes spherical (Ciliary mm.), 3. Pupil constriction (Sphincter pupillae mm.)

Question 10

Q: Definition of Saccades?

Answer 10

A: Rapid eye movements between objects/focus points to shift the fovea

Question 11

Q: Definition of Smooth Pursuit?

Answer 11

A: Ability of eyes to track a moving target to keep it focused on the fovea of the retina

Question 12

Q: Definition and direction description of Nystagmus?

Answer 12

A: Involuntary rhythmic eye movement; described by the direction of the quick phase (e.g., right or left beating)

Question 13

Q: The 3 Cranial Nerves that regulate gaze?

Answer 13

A: CN III (Oculomotor), CN IV (Trochlear), and CN VI (Abducens)

Question 14

Q: 3 common anatomical spaces CN III, IV, and VI pass through?

Answer 14

A: Subarachnoid Space, Cavernous Sinus, and Superior orbital fissure

Question 15

Q: Location of the Oculomotor (CN III) Nucleus?

Answer 15

A: Upper Midbrain at the level of the superior colliculi and red nuclei

Question 16

Q: Which muscle supplied by the Oculomotor nucleus is innervated contralaterally?

Answer 16

A: Superior Rectus (SR) muscle

Question 17

Q: Clinical result of a unilateral CN III Nuclear lesion?

Answer 17

A: Contralateral SR paralysis and bilateral ptosis (because CNIII nucleus supplies contralateral SR and bilateral Levator Palpebrae Superioris)

Question 18

Q: What is the Edinger-Westphal (EW) Nucleus?

Answer 18

A: The accessory CNIII nucleus that contains preganglionic parasympathetic fibers

Question 19

Q: Location of EW Nucleus fibers within the CN III nerve?

Answer 19

A: They run in the superficial and medial portion of the nerve

Question 20

Q: Clinical significance of EW nucleus fiber location?

Answer 20

A: They are the first to be affected by compression from an aneurysm (esp. Posterior Communicating Artery)

Question 21

Q: Location of the Trochlear (CN IV) Nucleus?

Answer 21

A: Caudal Midbrain at the level of the inferior colliculi

Question 22

Q: Unique features of the Trochlear nerve?

Answer 22

A: It is the only CN to exit the midbrain dorsally and the only CN with fibers that cross to the contralateral side after the nucleus

Question 23

Q: Clinical signs of CNIV (Trochlear) Palsy?

Answer 23

A: Vertical diplopia, hypertropia (if severe), and extorsion of the affected eye

Question 24

Q: Location of the Abducens (CN VI) Nucleus?

Answer 24

A: Mid-lower Pons, at the floor of the 4th ventricle

Question 25

Q: Why is CN VI susceptible to injury from hydrocephalus/meningitis?

Answer 25

A: It has a long path near the 4th ventricle

Question 26

Q: Clinical signs of CN VI (Abducens) Palsy?

Answer 26

A: Weak or absent abduction of the ipsilateral eye, causing exaggerated adduction (esotropia) at rest

Question 27

Q: Afferent pathway for the Pupillary Light Reflex?

Answer 27

A: Optic nerve (CN II) → Optic chiasm → Optic tract → Pretectal nucleus

Question 28

Q: Efferent pathway for the Pupillary Light Reflex?

Answer 28

A: EW Nucleus (Midbrain) → CN III → Ciliary Ganglion → Short Ciliary Nerves → Sphincter pupillae

Question 29

Q: Result of an Afferent Defect (e.g., in CN II of the Right eye)?

Answer 29

A: Light in Right eye: Decreased response in both pupils (no afferent signal to midbrain). Light in Left eye: Normal response in both pupils

Question 30

Q: Result of an Efferent Defect (e.g., in CN III of the Right eye)?

Answer 30

A: Light in Right eye: No direct response (Right eye can't constrict), Normal consensual response (Left eye constricts). Light in Left eye: Normal direct response (Left eye constricts), No consensual response (Right eye can't constrict).

Question 31

Q: What is the Horizontal Gaze Center?

Answer 31

A: The Paramedian pontine reticular formation (PPRF), located in the pons

Question 32

Q: Role of the Medial Longitudinal Fasciculus (MLF) in horizontal gaze?

Answer 32

A: It interconnects the CN VI (Abducens) nucleus in the pons to the contralateral CN III (Oculomotor) nucleus in the midbrain

Question 33

Q: Lesion of the CN VI Nucleus (e.g., Right Abducens Nuc.) causes?

Answer 33

A: Ipsilateral Lateral Gaze Palsy (loss of movement when looking to the side of the lesion; affects ipsi LR and contra MR)

Question 34

Q: Condition caused by damage to the MLF?

Answer 34

A: Internuclear Ophthalmoplegia (INO) (e.g., Left MLF lesion causes inability to adduct the Left eye when looking Right)

Question 35

Q: Definition of One-and-a-Half Syndrome?

Answer 35

A: Damage to an Abducens nucleus AND the ipsilateral MLF. Patient can only abduct the eye opposite the side of the lesion

Question 36

Q: Function of the Vestibulo-Ocular Reflex (VOR)?

Answer 36

A: Keeps the eyes fixed on an object during head movement by reflexively moving the eyes in the opposite direction of the head

Question 37

Q: Location of the Vertical Gaze Center?

Answer 37

A: Midbrain (Rostral Midbrain Reticular Formation and Pretectal Area / Periaqueductal gray)

Question 38

Q: Cause of Upward Gaze Palsy in Hydrocephalus?

Answer 38

A: Dilation of the 3rd ventricle, which pushes downward onto the periaqueductal gray (Vertical Gaze Center)