16 Anatomy of Orbit and Eye Flashcards
Fill in the missing labels:
Which artery carries the main blood supply to the orbit? Which artery does it branch off an how does it enter the orbit?
Opthalmic artery
Enters through optic canal
Which nerve brings general sensory information from the eye (including conjunctiva, cornea) ?
Trigeminal- opthalmic division Va
Which nerve brings special sensory information from the retina?
Optic- CN II
State 3 important structures that are close to the orbit. Why are these relevant clinically?
Cinically relevant: Infection and Trauma
Explain how an orbital fracture occurs.
Why might the patient be unable to gaze upwards on the affected side?
How?
Sudden increase intraorbital pressure- blunt object to the eye
Why patient unable to look up?
Eye stuck- orbital contents prolapsed into maxillary sinus
Trapped muscle and soft tissue
How will a patient with an orbital blow out fracture present?
- History of trauma to eye
- Sucken eye/ eye doesnt look up
- Pain and swelling- periorbital
- Numbness over cheek, lower eyelid and upper lip on affected side
- Double vision- worse on upward gaze
Fill in the missing labels:
Obicularis oculi= palpebral part
What are the 2 glands which can be found in the eyelid and what is their function?
Sebacious- eyelash follicles
Melbomian glands- secrete component of tear fluid, oily substance- prevents evaporation of tear film and tear spillage
How is a stye caused?
Blocked eyelash follicle/sebaceous gland (can be by infection)
How is a meibomian cyst formed? (not usually painful and can be excised if problematic)
Blocked meibomian gland
What is blepharitis?
Inflammation of lids (inc skin, lashes, meibomian glands)
Crusting on eyelids- usually fixed by washing and good eyelid hygiene
What is the orbital septum and what is its function?
What?
Fibrous thin sheet of tissue, continuous with tarsal plates (connective tissue) separating pre-septal and post-septal space
Outline the pathophysiology of periorbital cellulitis (infection occurring within eyelid tissue, superficial to orbital septum).
Causes?
Effect on eye function?
Management?
Causes?
Secondary to superficial infections
Secondary to bacterial sinusitis in children
Effect on eye function?
Unaffected
Management?
May be difficult to differentiate from orbital cellulitis- if in doubt urgently refer- high dose IV antibiotics+surgical drainage
Orbital (post-septal) cellulitis can be sight threatening. How might a patient present?
Proptosis/exopthalmos
Reduced+/painful eye movements
Reduced visual acuity (optic nerve)
Where can orbital cellulitis protentially spread to? What can this cause?
Intracranially- via cavernous sinus
- Cavernous sinus thrombosis
- Meningitis
Outline the venous drainage from the orbit.
Opthalmic veins–> cavernous sinus-> pterygoid plexus–> facial vein
What will happen is there is a blockage in the lacrimal sac/drainage system?
Eye will be watery- tears will spill out of eye = epiphora
Fill in the missing labels:
What does blinking achieve?
Distributes tear film across front of eye, rinsing and lubricating conjunctiva and cornea
Fill in the missing labels showing the layers of the eyeball:
How is the eyeball maintained in position?
What is the cornea? What does it do? Give an example of a pathology of the cornea.
Transparent mucous membrane covering anterior surface of eyeball
Highly vascular- small blood vessels in membrane
Pathologies:
Conjunctivitis: highly contagious
Haemorrhage from blood vessels- usually painless and will resolve
Name the structures within the eye that refract light as it enters:
- Cornea and tear film
- Lens
- Aqueous humour and vitreous humour
What do myopia and hypermetropia mean?
- Myopia= short-sighted
- Hypermetropia= long-sighted
Outline the accomodation reflex.
Focusing near objects
What is presbyopia?
Age related inability to focus near object
Lens= stiffer with age
Where are the rods and cones located in the retina and what do they do?
What is pin-hole testing and what can it be used for?
Check to see if decreased visual acuity is a refractive error
Acuity improved with pin-hole testing
What are the 2 fluid fill chambers that help to maintain the structure of the eye?
What is the most common cause of blindness in the UK?
Age-related macular degeneration
How is the aqueous humour produced and drained?
Produced:
Secreted by ciliary process in cilary body- nourishes lens and cornea
Drains:
Iridocorneal angle- between iris and cornea- into venous system (aka Schlemm’s canal)
What is glaucoma?
Optic nerve damage- secondary to raised intraocular pressure
Blocked drainage of aqueous humour
Differentiate between chronic and acute glaucoma.
How might patient with acute closed angle glaucoma present?
