Flashcards in Head And Neck Session 5 Deck (56):
What forms the superior border of the bony orbit?
Frontal and sphenoid
What forms the medial border of the bony orbit?
Ethmoid, maxillary, lacrimal and sphenoid
What forms the inferior border of the bony orbit?
Maxillary and zygomatic
What forms the lateral border of the bony orbit?
Zygomatic and sphenoid
What is found at the apex of the orbit?
Optic canal containing the optic nerve
What are the 4 important openings in the orbit?
Optic canal, superior and inferior orbital fissures and lacrimal fossa
Which aspects of the orbit are susceptible to Fx?
Medial and inferior
What is a blowout Fx of the orbit?
Orbital walls break allowing herniation of the orbital contents inferiorly into the maxillary sinus
Why might a pt with a blowout Fx have diplopia?
Inferior rectus muscle may have become tethered
How can a blowout Fx be identified on a radiograph?
Tear drop sign
Why is the blind spot on the optic disc?
There are no photoreceptors so light cannot be focused
Why do cataract sufferers wear sunglasses?
The lens becomes harder and flatter thus scattering light and causing glare
Which area of the eye gives the most accurate vision?
Where is the fovea located?
In the centre of the macula
What is the function of the iris?
Can constrict and relax to alter aperture of pupil
Where is the iris found?
Between lens and cornea
What makes up the inner layer of the eye?
The posterior lateral neural layer and deeper pigmented layers of the retina
Which layer of the retina contains photoreceptors?
Posterior lateral neural layer
What forms the middle vascular layer of the eye?
Choroid, ciliary body and iris
What are the components of the choroid?
CT and BV
What forms the outer fibrous layer of the eye?
Sclera and cornea
What is the function of the sclera?
Attachment of the eye to extraocular muscles
What is the function of the cornea?
Which bones form the orbit?
Frontal, zygomatic, sphenoid, maxilla, lacrimal and ethmoid
Why can retinal detachment occur?
Retina is derived from ectoderm but choroid is derived from mesoderm
What causes the painless loss of sight seen in retinal detachment?
Loss of bloodflow to retina
Why is photophobia seen in meningitis?
Optic nerve and brain have same layers of tissue so infection spreads
What feature of the optic nerve allows infection to lead to meningitis?
Venous drainage allowing retrograde infection
What are the layers of tissue common to the optic nerve and brain?
Pia mater, arachnoid mata and dura mata
Why does the optic nerve have the same layers of tissue as the brain?
It is a brain fact not a proper nerve
What is the function of the posterior segment of the eye?
Keeps it spherical
What is the function of the anterior segment of the eye?
Supply nutrients to the lens
Where is the anterior chamber of the eye found?
Between cornea and iris
Where is the posterior chamber of the eye located?
Between the iris and ciliary processes
What does the anterior segment contain?
What produces aqueous fluid?
How does aqueous fluid move to supply the avascular cornea and lens with oxygen and nutrients?
Moves through the iris
How does the aqueous fluid remove waste products from the cornea and lens?
Drains out through the trabecular meshwork into Schlamm's canal at the limbus then into 25-30 collector canals and finally into episcleral veins
What happens if the trabecular meshwork of the eye becomes blocked?
Drainage of aqueous humour impaired causing increase in volume in anterior chamber
Why does blockage of the trabecular meshwork of the eyes cause a painless loss of vision?
Increase in anterior chamber volume puts back pressure on vitreous body causing damage to the optic nerve
What is open-angle glaucoma?
Angle between cornea and iris increases due to accumulation of aqueous humour in the anterior chamber
Describe the passage of tears.
Formed in the lacrimal gland, moved inferiorly and medially across eye by opening and closing of the eyelids into lacrimal canal. Move into lacrimal sac, down nasolacrimal duct and into inferior meatus of nasal cavity
Where is the palpebral conjunctiva found?
On the inside of the eyelid
Where is the bulbar conjunctiva found?
Film covering the eye surface up to the limbus
In which conjunctiva can anaemia be identified?
What is he function of the eyelid?
To protect against injury, excessive light and dryness
In conjunctivitis, is the sclera implicated?
No, only the bulbar conjunctiva despite the red and inflamed appearance of the sclera
What is a myobium cyst?
Painless swelling of the tarsal gland
What is the treatment for a myobium cyst?
What is a stye?
Infection of the ciliary gland (usually staph aureus)
Why might Abx be given for a stye?
To prevent retrograde infection
What is the palpebral fissure?
Distance between the upper and lower eyelids
What would you look for O/E of the sclera?
Nodules, hyperaemia, discolouration
What would you look for O/E of the iris?
Colour, nodules, vascularity
How can the lacrimal apparatus be used to identify nasolacrimal blockage?
Gently press lacrimal sac on the inner orbital ring and material will move through punctuation in nasolacrimal obstruction