Eye Anatomy Flashcards
What is the fibrous layer that supports the eyelids?
Tarsal plate
What glands lie within the tarsal plate?
What do they do?
What pathology can develop in them?
Meibomian glands
Secrete oil into tear film to stop evaporation
Chalazion- granulomatous painless swelling
Which two muscles are responsible for eyelid movement? Which cranial nerves innervate them?
Orbicularis oculi- cranial nerve 7. Closes eye.
Lavatory palpebrae- CN3. Opens eye.
What is the junction of cornea and conjunctiva called?
Limbus
What is the thickening of the conjunctiva near the medial canthus called?
Semilunar fold
Name the tear glands
Describe their locations
Describe the drainage system of the eye
Accessory glands- produce most of the tears, located within eyelid and conjunctiva.
Lacrimal gland- located superolateral to eye. Responsible for reflexive tearing.
Drain out through small pores called lacrimal puncta on the medial lids. Flow down lacrimal tubing into inferior turbinate (nose).
In which situation would a lid laceration be concerning?
If it occurs in the nasal quadrant it can cause damage to tear drainage.
What structure is continuous with the sclera?
Cornea
What structure is formed by the sclera at the posterior of the eye?
Optic sheath
Name the three chambers of the eye and what structures they lie between
Anterior: cornea and iris
Posterior: iris and lens
Vitreous: Lens and retina
What is the purpose of aqueous humour?
Nourishes avascular cornea and lens
Describe the layers of the cornea
From top to bottom: Epithelium- protective Bowman’s layer Stroma- damage here can cause scarring Descemet’s membrane- basal lamina Endothelium
What is the purpose of the corneal endothelium?
What happens if damaged?
Pump to keep cornea dehydrated
If damaged can cause corneal oedema.
Cells don’t regenerate- too much damage means too few cells and need for corneal transplant
Describe the drainage of aqueous humour
Drains through anterior chamber angle via trabecular meshwork into Schlemms Canal.
What components collectively make up the uvea?
Iris, ciliary body, choroid plexus
What are the two functions of the ciliary body?
Controls shape of lens
Secretes aqueous fluid
What structures within the ciliary body change the shape of the lens?
Zonular fibres
Describe the structure and function of the choroid plexus
Bed of blood vessels living under the retina
Supplies nutrition to the outer 1/3 of the retina, which contains the rods and cones. Retinal detachments can seperate retina from choroid plexus and cause death of the rods and cones.
Describe the structure of the lens
Peanut M&M.
Capsule, cortex, nucleus.
What are the three types of cataracts?
Nuclear
Cortical
Subcapsular
What is the name for the difficulty “rounding out” the lens that commonly occurs after age 40, causing trouble reading?
Presbyopia
Describe the four layers of the retina innermost to outermost
Ganglion nerves- continuous with optic nerve
Photoreceptors
Choroid plexus- part of uvea
Optic sheath- continuous with sclera
What is the macula?
Pigmented area of retina responsible for central vision
Describe the location, function, and nutritional supply of the fovea
Central macula
Small pit involved in extreme central vision
Nutrition comes entirely from choroid- very vulnerable to retinal detachment
Name the seven bones that form the orbit
Frontal Ethmoid Lacrimal Maxillary Palatine Zygomatic Sphenoid
What is the orbital apex?
What Two important structures lie within it?
What surrounds these structures?
What are some pathologies are associated with injury here?
Posterior end of pyramid shaped orbit at the craniofacial junction where four walls of orbit meet.
Optic foramen, superior orbital fissure.
Annulus of Zinn
Orbital apex syndrome- damage to orbital apex. Involves optic nerve. Ptosis, blindness, and opthalmoplegia. (II, III, IV, V1, VI)
Cavernous sinus syndrome- orbital apex syndrome + more trigeminal involvement
Rochon-Duvigneaud syndrome- SOF damage. No blindness.
Where does the retina get it’s nutritional supply?
Anterior 2/3 from retinal vessels, posterior third from choroid.
Which is the only ocular muscle that doesn’t originate at the orbital apex?
Inferior oblique
Describe the regions of the conjunctiva
Bulbar- over sclera on eyeball
Forniceal- Fornix is the doubling back
Palpebral (marginal/tarsal/orbital)
What type of conjunctival injection is associated with inflammation of deep structures?
Ciliary flush/mixed
What conditions commonly cause follicular inflammation?
Adenovirus
Chlamydiae
Herpes simplex
Allergic
What can cause inflammation of the papillae?
Often chronic- allergic/mechanical irritation conjunctivitis
Anything really
Describe the classic features of adenovirus conjunctivitis
Abrupt onset
Unilateral=>bilateral
Follicles, diffuse hyperaemia, mucoserous discharge,
Preauricular adenopathy
Can get severe- keratitis with photophobia and ++pain. Pseudomembrane formation
Can have second phase corneal infiltrates
Name four common causative agents of bacterial conjunctivitis
Staph aureus
Staph epidermis
Strep pneumoniae
Haemophilus influenzae
Name the 6 extraocular muscles responsible for eye movement and their innervation
superior rectus - CNIII inferior rectus - CNIII medial rectus - CNIII lateral rectus - CNVI inferior oblique - CNIII superior oblique - CNIV
Name the 6 extraocular muscles responsible for eye movement and their actions
superior rectus - elevation and med rotation
inferior rectus - depression and lat rotation
medial rectus - adduction
lateral rectus - abduction
inferior oblique - elevation, lat rotation and abducts (up n out)
superior oblique - depress, med rotation and abducts (down n out)
Where do the 4 rectus muscles originate from and attach to?
Tendinous ring, sclera
What bony structure down the s.oblique travel thru?
Trochlear
