16 - Anatomy of the Eye Flashcards
What are the walls of the orbital cavity?
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- Pyramid shaped
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Which parts of the orbit are vulnerable to fracture and why?
- Impact to front of eye, e.g fist or ball, medial and inferior wals weakest so most susceptible
- Sudden increase in intraorbital pressure can lead to orbital blow out fracture of floor
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Why is the medial wall of the orbit slightly stronger than the floor, but what are the implications of this?
- Ethmoid bone very thin but ethmoidal air cells add strength
- Air cells can become infected, break through thin lamina papyracea and cause orbital cellulitis
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What are the nerves and blood vessels that run through the orbit?
- Optic canal: opthalmic artery and optic nerve
- Superior Orbital Fissure: CN II, VI, Va and superior opthalmic vein back to cavernous sinus
- Inferior Orbital Fissure: infraorbital nerve (Vb) and inferior opthalmic vein
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/328/413/a_image_thumb.png?1574322048)
What are some of the clinical presentations of an orbital blow out fracture?
- History of trauma to eye
- Periorbital swelling
- Double vision, worse on looking up
- Eye cannot gaze up
- Numbness over cheek, lower eyelid, upper lip on affected side (infraorbital nerve)
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What is the stucture of the eyelids?
- Tarsal plate
- Skin, muscles (OO, LPS)
- Glands (meibomian and sebaceous on lash follicle)
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What are the following pathologies of the eyelid?
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Meibomian Cyst: oily substance that stops evaporation of tears gets blocked. Self limiting, not painful, not on edge
Stye: painful, usually lash edge as infected lash follicles sebaceous glands
Blepharitis: inflammation of lids including skin, lashes and meibomian glands
All need good eye hygeine
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How does the anatomy of the orbit mean that superficial infetions don’t spread backwards?
- Orbital septum and tarsal plates separate subcut tissue and muscles from intra orbital contents
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/328/441/a_image_thumb.png?1574323179)
What is peri-orbital cellulitis?
- Due to superficial infection, e.g bite, wound, bacterial sinusitis
- Confined in front of orbital septum
- Oculomotor movements unaffected
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/328/451/a_image_thumb.png?1574323705)
What is orbital cellulitis?
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- Infection within the orbit affecting the muscles or the eye itself
- Could spread intracranially via orbital veins
- Need emergency IV and surgical drainage
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Label the different parts of the lacrimal apparatus and what is its function?
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- Lacrimal gland produces tears and is under PS control of facial nerve
- Lacrimal fluid goes over conjunctival sac and passes to lacrimal lake at medial angle of the eye
- Then goes to lacrimal sac and nasolacrimal duct into nasal cavity
- Epiphora if blockage
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/328/476/a_image_thumb.jpeg?1574324159)
What are the different layers of the eyeball?
- Outer: tough fibrous sclera with transparent cornea anteriorly. this layer is continuous posteriorly with dura mater covering optic nerve. Thin transparent layer called conjunctivae covers sclera up to cornea
- Middle: choroid which goes anteriorly as iris, ciliary body
- Inner: retina
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/328/487/a_image_thumb.jpeg?1574324740)
What is the diagnosis and treatment for both of these?
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- A: conjunctivitis, usually viral and due to blood vessels dilating. highly contagious. eye can feel gritty and uncomfortable
Hygeine and chloramphenicol eye drops
- B: subconjuctival haemorraghe. blood vessel ruptures but not painful. like a bruise but takes longer to heal
What may be a cause of conjunctivitis in the neonate and how would we treat it?
- Chlamydial infection from mother
- Systemic antibiotics like erythromycin
Label the following parts of the eye and shade the different chambers of the eye.
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