Orbit Flashcards
What movements do the eyes make to compensate for head tilt and what are the muscles responsible?
Involuntary rotational movements - medial and lateral rotation
Oblique muscles (superior and inferior)
What are the voluntary movements of the eye and muscles responsible?
Abduction/Adduction
Elevation/Depression
Rectus muscles (Superior, Inferior, Lateral, Medial)
What is the tendinous ring? (And what is the associated exception?)
Ring of connective tissue surrounding the optic canal and superior orbital fissure
Location of origin of most extraocular muscles
**Inferior oblique takes origin from the floor of the orbit
What are the actions of the superior and inferior rectus?
Superior rectus - raise, adduct, medially rotate
Inferior rectus - lower, adduct, laterally rotate
What are the actions of the superior and inferior oblique muscles?
Superior oblique - Lower, abduct, medially rotate
Inferior oblique - raise, abduct, laterally rotate
What does the resting position of the eye depend on, and what happens when there is damage to any one muscle?
The tonic activities of the muscles
Weakness of movement (depending on muscle); does NOT completely eliminate movement
What results from damage to CN VI?
Medial Strabismus (i.e. cross-eyed)
Dur to damage/paralysis of the lateral rectus
What results from damage to CN IV?
Inability to turn eye down and out
Patient compensates by tilting head to the opposite side
What results from damage to CN III?
Lateral Strabismus (i.e. wall-eyed) due to paralyzed medial rectus
Ptosis (Drooping eyelid) due to paralyzed Lev. Palp. Sup.
Dilated pupil (Mydriasis) due to paralyzed pupillary constrictor
What results from damage to the ciliary ganglion or short ciliary nerves?
Loss of parasympathetics of CN III
Mydriasis - dilated pupil
What is a blown pupil and what does it indicate?
Maximally dilated pupil
Indicates catastrophe - stroke, herniation, etc.
What are the Roof, Lateral, and Floor boundaries of the orbit?
Roof - Frontal bone
Lateral Wall - Zygomatic and Sphenoid
Floor - Maxiallary
What is the medial wall of the orbit comprised of?
Maxillary, Lacrimal, Ethmoid, Frontal, and Sphenoid bones
What foramina allow structures to enter the orbit?
The optic canal and superior orbital fissure
What two pathways allow structures to exit the orbit? (Excluding to nasal cavity)
Supraorbital notch
Infraorbital foramen
What pathways connect the orbit and the nasal cavity?
Anterior and Posterior ethmoidal foramina
Nasolacrimal duct
Describe the layers of the eyelid.
Skin - eyelashes and openings of sebaceous glands
Subcutaneous - CT that contains sebaceous glands
Obicularis Oculi (Palpebral part) - closes eye
What is a stye or horde’olum?
Obstruction or infection of sebaceous gland in the subcutaneous layer of the eyelid
What is the tarsal plate?
Fibrous CT “skeleton” of the eyelid
Contains Tarsal glands that keep tears in the eye and prevent their evaporation
What is a Chalazion?
Obstruction of the tarsal gland
What is the orbital septum?
CT layer continuous with periosteum of the orbit
What is the function of the medial and lateral check ligaments?
Prevent excessive rotation
What is astigmatism?
Irregularities of the cornea
What major arteries supply the eye and where do they originate?
Central artery of the retina
Posterior ciliary arteries (long and short)
Originate from the ophthalmic artery
What do the posterior ciliary arteries supply?
Pierce the sclera, blood to the choroid, photoreceptors
What does the central artery of the retina supply?
Neural retina
*End artery
Describe the choroid layer.
Highly vascular, pigmented
Provides oxygen, nutrients to photoreceptors
What occurs as a result of central retinal artery occlusion?
Blindness in the occluded eye
Most common cause is carotid artery atherosclerosis
Why can an increase in CSF pressure affect vision?
The dura and subarachnoid space extend around the optic nerve, and increase in pressure will push on the nerve.
Slow onset, headaches
What is papilledema?
Swelling of the optic disc
What is the dilator pupil?
Radial smooth muscle under sympathetic control
Dilates the pupil
What is the constrictor pupil?
Circular smooth muscle under parasympathetic control (CN III)
Constricts the pupil
