S8 L1 Applied Anatomy of the Orbit and Eye (My notes) Flashcards
- *Orbital Cavity:** pyramidal shaped with apex pointing posteriorly
- State the borders of the 4 walls
- What is the weakest parts of the orbital cavity?
Four bony walls
Base of pyramid faces anteriorly- tough orbital rim
Ethmoid bone contributes to medial wall
Maxillary bone contributes to floor
Anatomical Relations of the Orbit
- What is around it?
- What are the implications of this?
- *Clinical Application: Orbital Blowout Fracture**
- Cause
- Where is the fracture?
- What happens to the anatomy in this area?
- What does this patient struggle with?
- Treatment
- Management?
Orbital cavity - openings
- Optic canal
- Superior orbital fissure
- Inferior orbital fissure
Key Blood vessels of the Orbit and Eye
- Key arteries
- Key veins
Key Blood vessels of the Orbit and Eye:
Main arterial supply to orbit and eye ophthalmic artery (branch of ICA) and its branches, including central retinal artery (which supplies retina)
Main venous drainage of orbit and eye ophthalmic veins (superior and inferior) connections with cavernous sinus, pterygoid plexus and facial vein
Blood Supply to the Eye
Opthalmic artery supplies eye structures
Central retinal artery - supplies retina and draws supply from underlying choroid layer
Ciliary arteries - feed extensive capillary bed within choroid layer
Retina requires both central retinal artery and ciliary arteries to function properly
Eyelids:
- Explain the anatomy of the eye lids
Several glands within the eye
Diseases of the Eyelid
- Stye
- Meibomian cyst
Disease of Eyelid
- Blepharitis
What is the orbital septum? What is it continuous with?
How is the eye split into two?
What is the infection called ‘infront’ of the septum, what is it called ‘behind’ the septum?
Pre-septal
Post-septal
Orbital septum is continous with the orbital plate
Disease: Periorbital (pre-septal) Cellulitis
- Secondary to what…
- Confined to what…
- Sx, how to help rule it out
- Differential diagnosis
Disease: Orbital (post-septal) Cellulitis
- Where is this infection?
- Where has the infection spread from?
- Confined to what…
- Sx
- Differential diagnosis
**Reduced plus or minus painful eye movements
Reduced visual acuity
Contents of the Orbital Cavity
Tear film and Lacrimal Apparatus
- What makes up tear film?
- What is the role of the lacrimal apparatus?
- What does obstruction to drainage lead to?
Structure of the Lacrimal Apparatus
Anatomy of the Globe (eye ball)
- Position is maintained by?
What is the conjunctiva?
Disease affecting the Surface of the Eyeball (except cornea)
- Conjunctivities
- Sub-conjunctival haemorrhage
Structure of the eye-ball
- State the three layers
- Label cornea, lens, pupil, ciliary body, iris
Retina
- Structure
- Macula? Fovea? What are these?
Central Retinal Artery Occlusion
- What would you notice when looking at the retina and why?
- Sx
On looking:
Pale looking retina and cherry red spot (macula)
Underlying choroidal layer, blood supply is unaffected: remains perfused
Macular (thinnest part of the retina): so underlying choroid accentuated due to surrounding pallor of ischaemic retna
Globe of eye if filled with…
Explain the structure of the eyeball in relation to the anterior chamber and posterior chamber - what are they seperated by?
Production and Drainage of Aqueous Humour
Glaucoma
Two types:
- State their names, their pathologies, signs and sx
- Tx for the acutely presenting one
Optic nerve damage secondary to increase in intra-ocular pressure
More info on Acute Angle-Closure Glaucoma:
Opthalmological emergency
Presention example -
Older patient, acutely painful red eye, irregular oval-shape pupil (fixed), blurring of vision, halo’s around lights (due to corneal oedema), nausea, vomitting,
Tx: medical drugs to reduce IOP then surgical treatment.
Glaucoma
- What does this look like on fundoscopy?
Glaucomatous cupping
Damage to optic nerve head
How do we see?
What factors affect where the light lands/if it lands on the retina?
Accommodation Reflex
- What does this allow?
- How does the eye accommodate?
- What happens with age?
Phototransduction
- How does this work?
Action potentials propagated via retinal ganglion cells (RGCs)
RGC axons collect in area of optic disc forming the optic nerve
Optic disc = no photoreceptors (=blind spot”)
Action potentials propagated along visual pathway to occipital lobe for interpretation
Visual acuity
- Define
- Measured by?
- Normal vision is…
= ability of the eye to discern shapes and details of what you see
Measured formally using ‘Snellen Chart’
Read set of letters of increasingly smaller size: one eye at a time 6m distance
Normal vision = 6 / 6
Causes of decreased visual acuity?
What is the ‘red reflex’? How to check this?
When their is decrease visual acuity, what are the two major differentials?
Refractive?
abnormal corneal surface (astigmatism)
inability of lens to change shape
size of eyeball
Non-refractive? (More concerning!)
retinal or optic nerve problem
How to work out if decreased visual acuity is due to:
- Refractive error or non-refractive error?
