How does the eye see (anatomy) Flashcards
What protects the eye from a direct blow from any object of diameter greater than that of the orbital rim?
The orbital margins
Which parts of the orbit are most often affected in an orbital blow out fracture?
The medial wall of the orbit and the orbital floor (extremely thin 0.5-1mm)
-orbital rim remains in tact
When might the infraorbital canal/infraorbital NVB be damaged and what does this mean?
When the fractured zygoma rotates medially
-this will result in a general sensory deficit of the facial skin
Sphincter of the eye
Fibres surround the eyelids used to “screw up the eyes”
Orbicularis oculi
-used in blinking
Orbicularis oculi
Screw up the eyes
-within the eyelids, used in blinking
What is the purpose of the orbital septum?
Helps prevent the spread of infection from superficial (periorbital cellulitis) to deep (orbital cellulitis)
Muscle which raised the eyelid?
Levator palpebrae superioris
-contains skeletal and smooth muscle
Function of the tarsal glands?
Lipid secretion
What is the conjunctival formix?
Where the conjunctiva is reflected off the sclera and onto the internal aspect of the eyelid
Sympathetic nerve supply to the lacrimal gland?
CN VII
This ducts carries tears to the inferior meatus of the nasal cavity
Nasolacrimal duct
The 2 corneal reflections and their significance
The nasal and temporal (used clinically to track the symmetry of bilateral eye position/movements)
The 2 layers of the fibrous layer of the eye
The sclera
Cornea
Protective/attachment for the extra-ocular muscles
The sclera
Provides 2/3rds of the eye’s refractive power
The cornea
Controls the iris, the shape of the lens and the secretion of aqueous humor
The ciliary body
What is the choroid responsible for?
Nutrition and gaseous exchange for the other layers
is the common location of “floaters” caused by areas of liquefaction of the gel & clumping of collagen fibres/cells
Vitreous body
What is the anterior chamber?
The space between the cornea and the iris: contains aqueous
What is in the posterior chamber?
Contains the lens and aqueous humor
Located between the iris and the ciliary body
What is in the posterior segment of the eye?
Sclera, choroid, retina, vitreous body
The 3 layers of the retina
1) photoreceptors
2) ganglion cells (anterior to the photoreceptors)
3) The axons of the ganglion cells (lie anterior to photoreceptor cells and ganglion cells)
The retinal veins and retinal arteries lie anterior to the retina
Where are the visual cortices?
In the occipital lobes
Function of levator palpebrae superioris?
Lifts the upper eyelid
Where do all of the rectus muscles originate from?
The common tendinous ring (attached to bones surrounding the optic canal)
This muscle attaches to the anteromedial floor of the orbit
The inferior oblique
LR6
Lateral Rectus
CNVI (abducent nerve)
SO4
Superior oblique
CNIV (trochlear nerve)
AO3
All others
CNIII (oculomoter nerve)
Secretes aqueous
Ciliary body
Route of aqueous
1) circulates around lens within posterior chamber
2) Then into pupil and anterior chamber
3) Then reabsorbed into the scleral venous sinus (Canal of Schlemm) at the iridocorneal angle
Where is CNII formed from all of the axons leaving the retina?
Formed at the optic disc
What is the fundus?
The retina + macula + fovea centralis + optic disc
The opthalmic artery is a branch of which artery?
The internal carotid
How to tell the difference between the internal and external carotid artery? e.g. if they gave you a prosection of just the neck and you couldn’t tell?
The internal carotid has no branches in the neck!
The opthalmic artery travels in which canal?
The optic canal
Nasal branches of which artery contribute to Kiesselbach’s area?
Nasal branches of the opthalmic artery
The only vein draining the retina?
The central vein of the retina
What is an end artery?
An artery with insufficient anastamoses to maintain viability of the tissue supplied if arterial occlusion occurs
What is the danger triangle of the face?
The upper lip and the external nose
-here you can have retrograde spread of infection via superficial veins into the cranial cavity
The inferior opthalmic vein drains into which vein?
Drains into the superior opthalmic vein
-this then drains posteriorly into the cavernous sinus (via the superior orbital fissure)
Which arteries and veins are responsible for the “red eye” appearance in flash photography?
The ciliary arteries and veins of the uvea
The blind spot of the visual field corresponds to this
The optic disc
The only point of entry/exit from the retina for blood vessels and the axons of CNII?
The optic disc
Retinal artery occlusion and retinal vein occlusion
complete interruption of flow in a retinal artery branch/”branch” retinal vein = loss of an area of visual field corresponding to the area of ischaemia
b) complete interruption of flow of the central artery (end artery) or vein = monocular blindness
