Orbit

Question 1

List the boundaries of the orbit.

Answer 1

ROOF - Frontal (Orbital Part), Sphenoid (Lesser Wing)
MEDL - Ethmoid, Lacrimal, Frontal, Sphenoid
INFR - Maxilla, Zygomatic, Palatine
LATR - Zygomatic, Sphenoid (Greater Wing)

Question 2

Explain some of the more common orbital fracture sites.

Answer 2

Inferior orbital floor fractures are most prevalent, and injury could drag inferior rectus towards fractured line, which would lead to upward gaze in the affected eye.

Medial orbital wall fractures leads to air from the ethmoid air cells to go into the orbit, which can alter sensation when blowing the nose.

Question 3

What part of the dura does the ophthalmic n. (V1) help supply?

Answer 3

The tentorium cerebelli & faux cerebri

Question 4

Describe the lacrimal branch of V1

Answer 4

The Lacrimal N. (smallest branch) courses along upper border of lateral rectus muscle to lacrimal gland, then runs towards nose to innervate the conjunctiva and skin of upper lid.

Question 5

Describe the frontal n. of V1

Answer 5

The Frontal N. (largest branch) runs above levator palpebrae muscle and rostrally divides into the supraorbital n., which leaves orbit through the supraorbital notch to supply the upper lid, forehead, and scalp, while the supratrochlear passes over trochlea of superior oblique muscle to end in the conjuntiva of upper lid and forehead

Question 6

Describe the nasocillary n. of V1

Answer 6

The Nasocillary N. crosses optic nerve, coursing below superior rectus and superior oblique muscles to the medial wall of orbit. Its branches include: (1) a communication to the ciliary ganglion (2) the Long Ciliary to the iris and cornea (3) the infratrochlear, to medial angle of eye to innervate the conjunctiva, lacrimal sac, skin of lid and side of nose and (4) the anterior and posterior ethmoidal nerves to sinuses (frontal, ethmoid, sphenoid) and nasal cavity.

Question 7

Ophthalmic artery has anastomoses with what other artery?

Answer 7

Lacrimal A & Middle Meningeal A.

Question 8

What are the three modes of venous drainage?

Answer 8

Ophthalmic Vein - Cavernous Sinus
Facial Vein - PT Plexus
Infraorbital Vein - PT Plexus

Question 9

What is the relationship of nerves in the annulus of Zinn?

Answer 9

OUTSIDE
Lacrimal (V1)
Frontal (V1)
Trochlear (IV)

INSIDE
Superior (III)
Inferior (III)
Nasociliary (V1)
Abducens (VI)

Question 10

Muscle Table: Superior Rectus

Answer 10

Inn - Superior Oculomotor (CN III)
Org - Annulus of Zinn
Ins - SUP/ANT Sclera
Act - elevate, ADduct, invert

Question 11

Muscle Table: Inferior Rectus

Answer 11

Inn - Inferior Oculomotor (CN III)
Org - Annulus of Zinn
Ins - INF/ANT Sclera
Act - depress, ADduct, evert

Question 12

Muscle Table: Superior Oblique

Answer 12

Inn - Trochlear N. (CN IV)
Org - Body of Sphenoid
Ins - POST/LATR/SUP Sclera (from trochlea)
Act - depress, ABduct, invert

Question 13

Muscle Table: Inferior Oblique

Answer 13

Inn - Inferior Oculomotor (CN III)
Org - MED floor of orbit (lat to nasolacrimal groove)
Ins - POST/LAT/INF Sclera
Act - elevate, ABduct, evert

Question 14

Muscle Table: Medial Rectus

Answer 14

Inn - Inferior Oculomotor (CN III)
Org - Annulus of Zinn
Ins - ANT/MED Sclera
Act - ADduct

Question 15

Muscle Table: Lateral Rectus

Answer 15

Inn - Abducens (CN VI)
Org - Annulus of Zinn
Ins - ANT/LAT Sclera
Act - ABduct

Question 16

What are you testing when you ask a patient to look medially then elevate & depress?

Laterally then elevate & depress?

Answer 16

MED - Oblique (UP - IO, DOWN - SO)

LAT - Rectus (UP - SR, DOWN - IR)

Question 17

Describe the corneal reflex.

Answer 17

1. GSA fibers from V1 ophthalmic sense corneal trauma
2. BE fibers from VII close orbicularis oculi
3. GSE fibers from III oculomotor open eyelid (LPS muscle)

Question 18

Describe Horner’s Syndrome

Answer 18

Cause: loss of sympathetic innervation (anywhere along periarterial plexus, carrying sympathetic GVE postganglionic)

Symptoms: constriction of pupil, ptosis, anhydrosis, enopthalmous, flushing & increase of skin temperature.