OPHTHALMOLOGY: 480-482

Question 1

How does each branch of the autonomic system mediate pupillary control?

Answer 1

Parasympathetic - miosis, constriction

Sympathetic - mydriasis, dilation

Question 2

Describe the neuronal pathway for miosis.

Answer 2

1st neuron - Edinger Westphal nucleus to ciliary ganglion via CN III

2nd neuron - short ciliary nerves to pupillary sphincter muscles

Question 3

Describe the neuronal pathway for mydriasis.

Answer 3

1st neuron - hypothalamus to ciliospinal center of Budge (C8 - T2)

2nd neuron - exit at T1 to to superior cervical ganglion and travels along cervical sympathetic chain (near lung apex and subclavian vessels)

3rd neuron - plexus along internal carotid, through cavernous sinus; enters orbit as long ciliary nerve to pupillary dilator muscles

Question 4

What is the pupillary light reflex as observed on physical exam?

Answer 4

Illumination of one eye results in bilateral pupillary constriction (consensual reflex)

Question 5

Describe the pathway of the pupillary light reflex.

Answer 5

Afferent limb: light in either retina sends signal via CN II to pretectal nuclei in midbrain

Efferent limb: Pretectal nuclei signal bilateral Edinger Westphal nuclei which cause pupillary constriction via CN III

Question 6

Is Marcus Gunn pupil an afferent or efferent pupillary defect?

Answer 6

Afferent

Question 7

What does a “swinging flashlight test” show in Marcus Gunn pupil?

Answer 7

Decreased BILATERAL pupillary constriction when light is shone in affected eye relative to unaffected eye

Question 8

What are the two components of CN III and where are they generally located within the nerve?

Answer 8

Central - motor component

Peripheral - parasympathetic component

Question 9

What type of disease preferentially affects the central motor fibers of CN III first?

Answer 9

Vascular

Question 10

Why does vascular disease affect the central motor fibers of CN III first?

Answer 10

Decreased diffusion of oxygen and nutrients to the interior fibers from compromised vasculature that resides on the outside of the nerve

Question 11

What are signs of damage to the central motor fibers of CN III?

Answer 11

Ptosis, down and out gaze

Question 12

What type of damage preferentially affects the peripheral parasympathetic fibers of CN III first?

Answer 12

Compression from the outside (e.g. posterior communicating artery aneurysm, uncal herniation)

Question 13

What are signs of damage to the peripheral parasympathetic fibers of CN III?

Answer 13

Diminished or absent pupillary light reflex, blown pupil (often with down and out gaze)

Question 14

What are the two layers separated in retinal detachment?

Answer 14

Neurosensory layer of retina (that contains all the photoreceptors) from outermost pigmented epithelium (normally shields excess light and supports retina)

Question 15

What does retinal detachment lead to?

Answer 15

Degeneration of photoreceptors and subsequently vision loss

Question 16

What can retinal detachment be secondary to?

Answer 16

Retinal breaks, diabetic traction, inflammatory effusions

Question 17

Retinal breaks are more common in what kind of patient?

Answer 17

Patients with high myopia

Question 18

What precedes a retinal break and how should this situation be treated?

Answer 18

1. Posterior vitreous detachment (flashes and floaters)
2. Eventual monocular loss of vision like a “curtain drawn down”

Retinal break = surgical emergency

Question 19

What are the two things caused by age-related macular degeneration?

Answer 19

1. Metamorphopsia - distortion

2. Scotoma - eventual loss of central vision

Question 20

What are the two types of age-related macular degeneration?

Answer 20

Wet and dry

Question 21

Which is more common - wet or dry age-related macular degeneration?

Answer 21

Dry (nonexudative) > 80%

Wet (exudative) 10-15%

Question 22

Describe dry age-related macular degeneration.

Answer 22

Deposition of yellowish extracellular material (drusen) in and beneath Bruch membrane and retinal pigment epithelium leads to gradual decrease in vision.

Question 23

How can the progression of dry age-related macular degeneration be prevented?

Answer 23

Multivitamin and antioxidant supplements

Question 24

Which is more acute - wet or dry age-related macular degeneration?

Answer 24

Wet

Question 25

What causes wet age-related macular degeneration?

Answer 25

Bleeding due to choroidal neovascularization

Question 26

How do we treat wet age-related macular degeneration?

Answer 26

Anti-VEGF injections or laser

Question 27

The medial longitudinal fasciculus allows for cross talk between which two nuclei?

Answer 27

CN III and CN VI

Question 28

What is internuclear ophthalmoplegia?

Answer 28

Lesion in MLF so that eyes have trouble moving in the same horizontal direction

Question 29

How does the MLF allow for the eyes to move horizontally at the same time?

Answer 29

Highly myelinated - fast communication

Question 30

What type of patients tend to have lesions in the MLF?

Answer 30

Patients with demyelinating conditions (e.g. multiple sclerosis)

Question 31

What does right INO mean?

Answer 31

Means the right eye is paralyzed (directional term specifies the eye that cannot move)

Question 32

Describe what happens in internuclear ophthalmoplegia.

Answer 32

Lack of communication such that when the ipsilateral CN VI activates the lateral rectus, the contralateral CN III does not stimulate the medial rectus to fire

Question 33

Why does the abducting eye get nystagmus in internuclear ophthalmoplegia?

Answer 33

Ipsilateral CN VI overfires to compensate for contralateral CN III not firing

Question 34

Is convergence affected in internuclear ophthalmoplegia?

Answer 34

No