Pediatrics and Strabismus Vol. 2

Question 1

Which extraocular muscle has the largest arc of contact?

Answer 1

Inferior oblique (15 mm)

Question 2

Which extraocular muscles have the smallest arc of contact?

Answer 2

Superior and inferior rectus (6.5 mm)

Question 3

Which extraocular muscles only have a primary action?

Answer 3

Medial and lateral rectus muscle

Question 4

What is Sherrington’s law?

Answer 4

Increased innervation and contraction of an extraocular muscle causes decreased innervation and contraction of its antagonist

Question 5

Which deviation is typically measured to be larger: primary or secondary?

Answer 5

Secondary deviation (Due to increased innervation required to move the restricted eye to fixation)

Question 6

What is primary deviation?

Answer 6

Amount of misalignment when normal eye is fixating

Question 7

What is secondary deviation?

Answer 7

Amount of misalignment when restricted eye is fixating

Question 8

Where does the smooth pursuit pathway start within the brain?

Answer 8

In the striate cortex

Question 9

Why is there a tonic convergence of the ayes in the normal, resting state?

Answer 9

Because the eyes are divergent in the total paralysis state

Question 10

Where are the cells responsible for initiation of saccades located?

Answer 10

Within the pontine reticular formation (burst cells)

Question 11

What does the striate cortex receive input from in the smooth pursuit pathway?

Answer 11

Lateral geniculate bodies

Question 12

In the smooth pursuit pathway, what nuclei transmit input to the oculomotor nuclei?

Answer 12

Vestibular nuclei

Question 13

What is the primary thalamic nucleus connecting the retina and striate cortex?

Answer 13

Lateral geniculate body

Question 14

What Brodmann area is associated with the primary visual cortex?

Answer 14

Brodmann area 17

Question 15

Where do approximately 90% of the retinal ganglion cells terminate?

Answer 15

Lateral geniculate body (LGN)

Question 16

What are M neurons particularly responsive to?

Answer 16

Moving objects

Question 17

What are the two primary neural systems of the retinogeniculocortical pathway?

Answer 17

Magnocellular (M) and parvocellular (P)

Question 18

Where does the magnocellular system (M) originate?

Answer 18

Parasol retinal ganglion cells

Question 19

Where does the parvocellular system (P) originate?

Answer 19

Midget ganglion cells

Question 20

What neural system accounts for approximately 80% of retinal input?

Answer 20

Parvocellular system (P)

Question 21

What is the primary function of the parvocellular system (P) system?

Answer 21

Object detail (color, shape, depth,etc.)

Question 22

Where does the koniocellular system (K) originate?

Answer 22

Bistratified ganglion cells

Question 23

What is the primary function of the koniocellullar system (K)?

Answer 23

Color vision (especially blue)

Question 24

Which layers of the LGB are parvocellular? Magnocellular?

Answer 24

1 to 4 (P), 5 to 6 (M)

Question 25

What layers of the LGB receive input from the contralateral nasal retina?

Answer 25

1, 4, and 6

Question 26

Which layers of the LGB receive input from the ipsilateral temporal retina?

Answer 26

2, 3, and 5

Question 27

During gestation, when does maximal ganglion retinal cell count occur?

Answer 27

Week 18

Question 28

When does retinal ganglion call loss begin to occur during gestation?

Answer 28

Week 30 (occurs until first few months of life after birth)

Question 29

What is normal estimated visual acuity at birth?

Answer 29

20/400

Question 30

Where is the primary site of amblyopia thought to be located?

Answer 30

Primary visual cortex