9 - Head & Neck - The Eye Flashcards
Which bones form the orbit?
- Sphenoid bone
- Ethmoid bone
- Frontal bone
- Lacrimal bone
- Maxillary bone
- Zygomatic bone
List the boundaries of the orbit:
Apex = Optic canal Roof = Frontal + Sphenoid Floor = Maxillary + Zygomatic Lateral = Zygomatic + Sphenoid Medial = Lacrimal + Ethmoid + Maxillary + Sphenoid
Which wall of the orbit is the weakest?
Base of orbit
Name the tissue of the eye to which the extra-ocular muscles attach to:
Sclera
Why does the eye appear red if patient has conjunctivitis? Why does conjunctivitis not affect the iris or pupil?
- Blood vessels in the conjunctivae dilate due to inflammation
- Conjunctivae covers sclera up to the cornea (does not cover pupil/iris)
Which structures of the eye are avascular? How do they recieve nutrients?
- Lens
- Cornea
via Aqueous humour
Name the tissues which form the outer tough layer of the eyeball:
- Sclera
- Conjunctiva
Name the tissues which form the middle layer of the eyeball:
- Choroid
- Ciliary body
- Iris
Which structure makes up the inner layer of the eyeball?
Retina
Which layer of the eyeball contains a rich network of blood vessels?
Middle layer (mainly in choroid)
Name the 3 chambers of the eyeball, and the fluid which fills each:
1) Anterior chamber - Aqueous humour
2) Posterior chamber - Aqueous humour
3) Vitreous chamber - Vitreous humour
How does the anterior chamber of the eye communicate with the posterior chamber?
Through the pupil
Which structures of the eye secrete aqueous humour?
- Ciliary body
- Ciliary processes
What are the roles of the ciliary body?
- Controls thickness and focus of lens
- Varies opening of trabeculae meshwork
- Secretes aqueous humour
Describe the drainage of aqueous humour into the venous system:
- Through Irido-corneal angle
- Into canal of Schlemm via trabecular meshwork
Name the 3 canals which open into the orbit, and which bone they lie in:
- Superior orbital fissure
- Inferior orbital fissure
- Optic canal
= Sphenoid bone
Which structures run in the optic canal?
- Optic nerve
- Ophthalmic artery
Which structures run in the superior orbital fissure?
- Oculomotor nerve (sup. + inf. branches)
- Trochlear nerve
- Abducens nerve
- Ophthalmic nerve (frontal, lacrimal + nasociliary branches)
- Superior ophthalmic vein
Which structure runs in the inferior orbital fissure?
- Inferior ophthalmic vein
What is a ‘blow-out fracture’?
Fracture of orbit, usually medial wall + floor
What is Reiter’s syndrome?
Conjunctivitis, arthritis + urethritis
- Autoimmune reactive arthritis due to bacterial infection
What is the classical presentation of an Oculomotor nerve lesion?
- Ptosis
- Fully dilated pupil
- ‘Down-and-out’ eye
Why may someone with a facial nerve palsy have to consistently dab eye due to constant weeping?
Paralysis of orbicularis oculi
= Inferior eyelid pulls away, exposing cornea
= Constant irritation
= Increased lacrimal secretion
What is cataracts? Who does it commonly affect?
Opacification of the lens
= reduced vision
= reduced acuity
= reduced contrast sensitivity
Diabetics, smokers, elderly
What is Presbyopia?
The natural long-sightedness occurring with age, due to loss of elasticity of lens
How does retinal detachment present? What causes these symptoms?
Blurring of vision, black dots/streaks, sudden flashes of light
Retina detaches from choroid (which contains blood supply), leading to avascular necrosis of retina.
Name the most common type of glaucoma:
Open-angle glaucoma
What is open-angle glaucoma?
Increased intra-ocular pressure due to blockage within trabecular meshwork of eye = damaged optic nerve
Develops slowly and painlessly.
Signs = optic disc cupping, loss of visual field
What is the treatment for open-angle glaucoma?
- Eyedrops to reduce aqueous humour production: beta-blockers ie Timolol
- Surgery (trabeculectomy)
What is closed-angle glaucoma?
Rapid increase in intracranial pressure due to narrowing of irido-corneal angle
