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Neurology - Anatomy and Physiology > Ophthalmology - Physiology > Flashcards

Ophthalmology - Physiology Flashcards

1
Q

What is the anterior chamber of the eye?

A

Anterior to the iris

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2
Q

What is the posterior chamber of the eye?

A

Posterior to the iris

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3
Q

Where does aqueous humor originate from?

A

Ciliary epithelium

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4
Q

Where does aqueous humor flow?

A

Flows from ciliary epithelium anteriorly –> in between iris and lens to anterior chamber.

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5
Q

Where does aqueous humor flow from anterior chamber?

A

Through trabecular meshwork –> Canal of Schlemm.

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6
Q

What happens when ciliary bodies contract?

A

Zonular fibers LOOSEN. Lens thickens. (Accomodation)

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7
Q

What happens when ciliary bodies relax?

A

Zonular fibers are pulled tight. Lens thins.

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8
Q

What happens to light entering the eye?

A

Focuses on point on the retina.

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9
Q

What happens if the eye is too short for the refractive power of cornea and lens?

A

Light is focused behind retina. Hyperopia. Blurry images up close.

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10
Q

What happens if the eye is too long for the refractive power of cornea and lens?

A

Light is focused in front of retina. Myopia. Blurry images far away.

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11
Q

Myopia is called?

A

Nearsighted - can see NEAR things.

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12
Q

Hyperopia is called?

A

Farsighted - can see FEAR things.

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13
Q

Astigmatism is caused by?

A

Abnormal curvature of the cornea. Different refractive power at different axes.

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14
Q

What is the primary defect in presbyopia?

A

Lens is less elastic due to age related changes - unable to thicken. Accomodation is impaired (harder to focus on near objects). –> reading glasses.

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15
Q

What is miosis?

A

Constriction.

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16
Q

Is constriction of pupils sympathetic or parasympathetic?

A

Parasympathetic.

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17
Q

Which neurons are responsible for constriction of pupils?

A

1st order neuron: From edinger-westphal nucelus to ciliary ganglion via CN III.
2nd order neuron: From short ciliary nerves to pupillary sphincter muscles

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18
Q

What are the steps of the pupillary light reflex?

A
  1. Light in either retina sends a signal via CN II to pretectal nuclei in midbrain
  2. Pretectal nuclei activates bilateral edinger-westphal nucleus
  3. Pupils constrict bilaterally
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19
Q

What is mydriasis?

A

Dilation

20
Q

Is mydriasis sympathetic or parasympathetic?

A

Sympathetic.

21
Q

What is the first neuron involved in pupillary dilation?

A

Hypothalamus to ciliospinal center of Budge (c8-T2)

22
Q

What is the second neuron involved in pupillary dilation?

A

Exits at T1 to superior cervical ganglion (travels along cervical sympathetic chain near lung apex, subclavian vessels).

23
Q

What is the 3rd neuron involved in pupillary dilation?

A

Plexus along internal carotid, through cavernous sinus; enters orbit as long ciliary nerve to pupillary dilator muscles.

24
Q

What else do the sympathetic fibers that innervate pupillary dilators innervate?

A

Smooth muscle of eyelids (minor retractors) and sweat glands of forehead and face.

25
Q

What is a Marcus Gunn pupil?

A

Afferent pupillary defect. Defect of bilateral pupil constriction.
- when light shines in affected eye, bad constriction
- when light shines in unaffected eye, good constriction
(swinging flashlight test).

26
Q

What lesion causes Marcus Gunn pupil?

A

Optic nerve damage or severe retinal injury.

27
Q

What muscle does CN VI innervate?

A

Lateral Rectus: Abduction.

28
Q

What muscle does CN IV innervate?

A

Superior Oblique: Inward and Downward.

29
Q

What muscles does CN III innervate?

A

Superior Rectus, Inferior Oblique, Superior Rectus
Medial Rectus Medial Rectus
Inferior Rectus Inferior rectus

30
Q

What does CN VI damage cause?

A

Medially directed eye that cannot abduct

31
Q

What does CN IV damage cause?

A

Eye moves upward, particularly w/ contralateral gaze, and head tilt towards size of lesion. (problems going down stairs). May present w/ head tilt in opposite direction.

32
Q

When CN III is damaged, what motor defects arise?

A

Ptosis, down and out gaze.

33
Q

What causes damage to motor output of CN III?

A

Primarily vascular disease; eg, DM (glucose/sorbitol). Decreased diffusion of oxygen and nutrients.

34
Q

When parasympathetic output of CN III is damaged, what are the defects?

A

Diminished or absent pupillary light reflex, blown-pupil, often w/ down and out gaze.

35
Q

What causes damage to parasympathetic output of CN III?

A

Fibers are on the periphery and are first affected by compression: posterior communicating artery aneurysm, uncal herniation.

36
Q

What coordinates conjugate horizontal gaze?

A

MLF.

37
Q

What nerves must cross-talk for conjugate horizontal gaze?

A

CN VI and CN III.

Eg when you look to the RIGHT, Right eye moves laterally (CN6), and left eye moves medially (CN3

38
Q

Why is the MLF highly myelinated?

A

Must communicate quickly so eyes move at the same time.

39
Q

What happens if there is a lesion in the MLF?

A

internuclear opthalmoplegia (INO), conjugate horizontal gaze palsy.

40
Q

If a person w/ INO tries to look right, what happens?

A

Right eye looks right (CN 6abducts)
Left eye doesn’t. (No communication to CN 3)
Right eye gets nystagmus because CN 6 overfires to stimulate CN 3.

41
Q

Does “right INO” mean right eye has nystagmus, or right eye isn’t moving?

A

Right eye isn’t moving. Refers to which eye isn’t moving upon contralateral gaze.

42
Q

In what disease is INO classically seen?

A

MS.

43
Q

What is the effect of a1 receptors on the eye?

A

Pupillary dilator muscle –> mydriasis

44
Q

What is the effect of a2 receptors on the eye?

A

decrease aqueous humor production

45
Q

What is the effect of B2 receptors on the eye?

A

Ciliary muscle relaxation

Decrease aqueous humor

46
Q

What is the effect of M3 receptors on the eye?

A

pupillary sphincter muscle contraction –> miosis

Ciliary muscle contraction –> accomodation

Neurology - Anatomy and Physiology (19 decks)

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