Ophthalmology Flashcards
The space between the eyelids is the?
(The orbicularis oculi is arranged as a ring of fibres around this).
Palpebral aperture or fissure.
(contraction of orbicularis oculi causes the eyelids to close).
Opening of the eyelids is primarily performed by?
Levator muscle of the upper lid.
(Tenuous fibres in the lower lid also retract lower lid).
The levator muscle of the eye extends from where?
an attachment at the orbital apex to the tarsal plate and skin (forms eye crease).
Eyelids are securely attached at either end to the bony orbital margin by?
The medial and lateral palpebral (or canthal) ligaments.
Trauma to the medial palpebral/ canthal ligament causes what?
Eyelid to move anteriorly and laterally.
Impairs both function and cosmesis.
What nerve(s) is associated with the afferent limb of the blink reflex?
- Optic nerve.
- Trigeminal nerve (CN V).
- Auditory nerve.
What nerve(s) is associated with the efferent limb of the blink reflex?
- Facial nerve.
What is the posterior lamella of the eyelids composed of?
- Conjunctiva.
- Semi-rigid tarsal plate.
What is the anterior lamella of the eyelids composed of?
- Skin.
- Orbicularis oculi.
Meibomian glands produce which component of the tear film?
Oily lipid component.
Sensory innervation of the upper lid is supplied via what nerve?
Ophthalmic division of the trigeminal.
Sensory innervation of the lower lid is supplied via what nerve?
Maxillary division of the trigeminal.
Orbicularis oculi receives innervation via?
Facial nerve (CN VII).
Levator muscle of the upper lid is supplied by which nerve?
Oculumotor nerve (CN III).
Which examination finding of the lids would suggest facial nerve palsy?
Ectropion of the lower lid, but NOT ptosis.
(palsy of CN III WOULD cause a ptosis).
Palsy of which nerve would cause a ptosis?
CN III - oculomotor.
Eyelid arterial supply via the face comes from which artery?
External carotid artery.
Eyelid arterial supply via the orbit comes from which artery?
Internal carotid artery.
Lymphatic fluid from the eyes drains into which groups of nodes?
- Pre-auricular.
- Submandibular.
what are the two layers of the conjunctiva?
- Epithelium.
- Stroma (posterior).
Describe the epithelium of the conjunctiva.
Contains goblet cells which secrete the mucin component of the tear film.
Sensory innervation of the conjunctiva is supplied via what nerve?
Ophthalmic division of trigeminal.
What is the name given to the area where the cornea and sclera merge?
The limbus ( at the corneal edge).
Name the layers of the cornea.
- Epithelium.
- Stroma.
- Endothelium.
The cornea is avascular. True or false?
True.
It derives its nutrition by diffusion from blood vessels at the limbus, aqueous humour and the tear film.
The cornea is innervated by?
Ophthalmic division of trigeminal.
Main functions of the cornea.
- Protection against micro-organisms.
- Transmission and focusing of light.
What secretes most of the aqueous component of the tear film?
lacrimal gland.
The lacrimal gland is innervated by?
Parasympathetic fibres carried by the facial nerve.
The uvea is composed of?
Iris, ciliary body (anteriorly) and choroid (posteriorly).
What lines the posterior surface of the iris?
Pigment cells.
Main functions of the iris?
- Control light entry to retina.
- Reduce intraocular light scatter.
Describe the mechanism behind pupil dilation.
Contraction of radial smooth muscle due to sympathetic innervation.
Describe the mechanism behind pupil constriction.
Contraction of the sphincter pupillae muscle (ring of smooth muscle around pupil) due to parasympathetic innervation (CN III).
Which part of the ciliary body is the site in which aqueous humour is formed?
Ciliary processes.
What happens when muscle fibres within the ciliary body contract?
ACCOMODATION (near vision) - Reduced tension on zonules > lens becomes more convex.
Accommodation is due to innervation by which nerve?
Parasympathetics of oculomotor nerve.
What shape should the lens be in distance vision?
Flat.
near - convex / round.
The choroid is composed of?
Blood vessels, connective tissue and pigment cells.
Where is the choroid located?
Between sclera and retina.
What is the function of the choroid?
Provide oxygen and nutrition to outer retinal layers.
What is presbyopia?
Failure of accommodation associated with ageing.
How does presbyopia occur?
Loss of capsule elasticity and lens deformability.
Where is the anterior chamber located?
Space between cornea and iris.
Where is the posterior chamber located?
Space posterior to the iris and anterior to the lens.
What fills the posterior and anterior chambers?
Aqueous humour.
Neural control of aqueous humour formation is via?
Sympathetic autonomic nervous system (beta receptors).
Describe the pathway of aqueous humour circulation.
Produced in ciliary body in posterior chamber > pupil > anterior chamber > trabecular meshwork > Schlemm’s canal > veins.
Where is Schlemm’s canal located?
Corneoscleral limbus.
Describe the trabecular meshwork of the eye.
Specialised tissue in anterior chamber (between iris and cornea).
What is the vitreous body composed of?
- 99% water, collagen fibrils, hyaluronan.
Where is the vitreous particularly adherent to the retina?
Optic disc and ora serrata.
What is the ora serrata?
Junction between retina and ciliary body.
How does vitreous deterioration cause retinal detachment?
Vitreous body attached to retina, particularly at optic disc and ora serrata. Degeneration causes it to pull on the retina, causing it to tear and detach.
function of the retina.
Converts focused light images into nerve impulses.
What is the retina composed of?
- Neurosensory retina.
- Retinal pigment epithelium.
Which area of the retina provides for central vision?
Macula.
The rest is for peripheral vision.
Fovea function?
Sharp central, high quality vision.
What is concentrated at the macula and why?
Cones (photoreceptors) for visual acuity i.e. vision in bright light and colour appreciation.
Rods are distributed throughout the entire retina (mostly peripheral), why?
Vision in low light levels and detection of movement.
Blood is supplied to the retina from?
Central retinal artery and vein.
Choroid.
What passes through superior orbital fissure?
- Lacrimal, frontal and nasociliary nerves (ophthalmic division of CN V).
- CN III, IV, VI.
- Superior ophthalmic vein (passing to cavernous sinus).
What passes through inferior orbital fissure?
- Exiting inferior ophthalmic vein.
- Maxillary division of CN V.
Compression at the orbital apex may result in what signs?
- Loss of corneal sensation.
- Reduced ocular movement.
- Impaired visual function.
- Proptosis.
How may pupil dilation be achieved?
- Anti-cholinergics - Tropicamide (2 hours), Cyclopentolate.
- Sympathetic agonist - Phenylephrine.
- Atropine (1 week).
Pituitary tumour causes what visual field defects?
Bitemporal hemianopia.
A unilateral lesion posterior to the optic chiasm would cause what visual field defect?
Hemianopia on contralateral side.
Occlusion of the arterial supply to the visual cortex would cause what visual field defect?
Bilateral field loss with macular sparing (i.e. only central vision retained).
What is visual acuity?
The measure of the ability of the eye to see that two close objects are in fact separate.
Visual acuity is tested using?
Snellen chart.
Colour appreciation is tested using?
Ishihara colour plates.
Fluorescein mixes with the tear film, adhering to what?
Areas of epithelial loss (ulcer or abrasion).
Fluorescein is best visualised using what colour of light?
Blue.
How is unilateral optic nerve pathology (i.e. relative afferent pupil defect) tested?
Swinging flashlight test.
What is the main cause of diminished red reflex?
Cataract.
Monocular abnormal visual fields suggests?
Optic nerve or retinal pathology.
Binocular abnormal visual fields suggests?
Intracranial disease.
What is the role of the aqueous layer of the tear film?
- Smooths optical interface.
- Washes away debris.
- Conveys oxygen and antibacterials to corneal and conjunctival surfaces.
What is responsible for secreting approximately 95% of the aqueous component of the tear film?
Main lacrimal gland.
+ additional secretion by accessory glands in conjunctiva
Inner mucinous layer of tear film is produced mainly by?
Conjunctival goblet cells.
What is the role of the inner mucinous layer of the tear film?
Provides a hydrophilic attachment for the aqueous component.
Uveitis is associated with which systemic conditions?
- Inflammatory bowel disease.
- Sarcoidosis.
- Seronegative arthritis (psoriatic, rheumatoid, reiter’s syndrome).
- Ankylosing spondylitis.
- SLE.
- TB, syphilis, toxoplasmosis, Herpes (zoster and simplex)
- etc etc
Symptoms and signs of uveitis?
- Painful red eye.
- Photophobia.
- Intraocular inflammation e.g. cells in anterior chamber.
What is episcleritis?
Inflammation between conjunctiva and sclera.
- Usually affects young, women.
