Eyes Flashcards
What muscle controls the closing of thee eyelid and what innervates it
Orbicularis oculi muscle
Facial nerve
What innervates the eyelid closing muscles
Oculomotor, facial nerve and some sympathetic innervation
What is the function of the meibomian glands
Produce meibum (lipid part of the tear film)
What is the function of the eyelid
- Protects eye from trauma
- Blinking distributes tear film and removes debris from ocular surface
What is the function of tear film
Provides nutrition and hydration of the ocular surface
What is the function of the nasolacrimal system
Drains tear film
Define entropion
Inward turning of all or parts of the eye margin
Define Ectropion
Outward turning of the rim of the eyelid
List conditions of the cilia
- Distichiasis
- Ectopic cilia
- Trichiasis
Define Distichiasis
Extra eyelashes emerging from meibomian gland orifices
Define ectopic cilia
Cilia arise from follicle inside or near meibomian gland and emerge through the conjunctiva surface of eyelid
Define Trichiasis
Normally located cilia but abnormally directed hair which contact the ocular surface
What is the function of the third eyelid
- Protects ocular surface
- Distributes tear film and removes debris
- Contains immunoglobulin secreting plasma cells
What are the layers of tear film
Lipid
Aqueous
Mucin
Origin of the lipid part of the tear film
Meibomian glands
Origin of the aqueous part of tear film
Orbital and nictitans glands
Origin of muni part of tear film
Conjunctival goblet cells
Function of tear film
-provides nutrients to the ocular surface
-protects the ocular surface from desiccation and bacteria
-lubrictes the ocular surface
Provides smooth transient ocular surface
Describe the anatomy of the cornea
- stratified, squamous non-keratinised epithelium
- basement membrane
- collagenous stroma
- Descement’s membrane
- endothelium
How is corneal transparency maintained
Low cell density
Relatively dehydrated state
Smooth optical surface
Lacks keratinisation, blood vessels and melanin
Very regular arrangement of collagen fibrils
What is keratoconjunctivitis
Dry Eye
Is a local immune mediated destruction of orbital and nictitans lacrimal glands
What is a corneal ulcer
Disruption of the corneal epithelium and stroma
How do stromal corneal ulcers heal
Healing of the storma starts after cornel epithelium is healed
Fibroblasts migrate in and new collagen is laid down
Vascularisation occurs causing scar tissue to be formed
What makes up the anterior uvea
Iris and ciliary body
What makes up the posterior uvea
Choroid
What is the function of the iris
Controls the amount of light entering the eye and forms part of the blood-ocular barrier
What is the function of thee ciliary body
Controls accommodation and produces aqueous humour, anchors lens, makes up part of the blood aqueous barrier
Name the 5 layers of the choroid
Suprachoroidiae Large vessel layer Medium vessel layer Choriocapillaris Bruch’s membrane
What is the function of the choroid
Blood supply for retina
Part of blood ocular barrier
Includes the tapetum
What makes up the blood ocular barrier
Blood aqueous Barrier and blood retina barrier
What is uveitis
Inflammation of the uvea
How is aqueous humour produced
Is produced by the ciliary processes by diffusion, ultrafiltration and active secretion
How is aqueous humor drained
By the uveal trabecular mesh work
What is a glaucoma
Where increased intraocular pressure results in damage to the retina and optic nerve with loss of vision
Describe posterior lens luxation
Is when the lens moves backwards into the eye
Describe anterior lens luxation
When the lens moves forward and can block the flow of aqueous humour and can cause secondary glaucoma
What causes lens luxation
The zonule fibres weaken and break causing lens luxation
What causes the development of cataracts
When the amount of protein in the composition of the lens changes
Define exophthalmos
Anterior displacement of the globe (bulging or protruding eyeballs )
Define enophthalmos
Posterior displacement of globe
Define hydrophthalmos
Congenital glaucoma
Define microphthalmos
A severe developmental disorder of the eye which one or both eyes are abnormally small and have atomic malformations
Define anisocoria
Unequal pupil size
Define miosis
Excessive constriction of the pupil of the eye
Define mydriasis
Dilation of the pupil of the eye
Define strabismus
Abnormal alignment of the eyes (the condition of having a squint)
Define nystagmus
Rapid involuntary movements of the eyes
What are the important retinal layers
Nerve fibre layer Ganglion cell layer Outer nuclear layer Photoreceptors layer Retinal pigments epithelium
How many layers make up the retina
10
What is the fundus
The portion of the posterior segment of the eye that is viewed with the ophthalmoscope
What nerve provides sensory innervation to the eyelids
Trigeminal nerve
What tear producing gland is present at e base of the third eyelid
Nictitans gland
What is the purpose of the lipid layer of the tear film
Limits evaporation from the surface
From where do corneal stem cells originate
Limbus
How would you differentiate nuclear sclerosis from a cataract
Distant direct ophthalmology
From where does the developing lens (in the foetus) obtain its nutrition
Tunica vasulosa lentis
What are the black masses suspended from the edge of the pupil in the horse eye
Corpora nigra
