Eye Anatomy Flashcards
What are the parts of the fibrous coat of the eyeball?
Sclera & cornea
What are the parts of the vascular coat of the eyeball?
Choroid
Ciliary body
Iris
What are the parts of the sensory coat of the eyeball?
Retina
What is the function of the sclera?
Gives attachments to the extrocular muscles
How much of the fibrous coat does the sclera make up?
5/6th
opaque
What is the function of the cornea?
Allows light to enter the eye
How much of the fibrous coat does the cornea make up?
1/6th
Transparent
What is the function of the choroid?
Supplies blood to outer layer of retina
What is the function of ciliary bodies?
Produces Aqueous humor
Suspends the lens
What is the function of the iris?
Controls the diameter of the pupil & therefore the amount of light entering the eye
What is the function of the retina?
Has rods & cones which enable us to see
Where is vitreous humor found?
Posterior segment
Where is AH found?
Anterior segment
What is the structure of the lens described as?
Biconvex crystalline structure that is suspended from the ciliary body by suspensory ligaments
What is the function of the AH?
It maintains intraocular pressure
What is the function of VH?
Cushions the retina
What is the anterior segment further divided into?
Anterior & posterior chamber
Where is the Anterior chamber found?
In front of the iris
Where is the anterior segment found?
In front of the lens
Where is the posterior chamber found?
Behind the iris
Where is the posterior segment found?
Behind the lens
At the angle of the anterior chamber where does AH drain?
Via trabecular meshwork into the Schlemms canal
What are the names of the 3 entry/exit points in the bony orbit?
Optic foramen
Superior orbital fissure
Inferior orbital fissure
Which paranasal sinuses is the orbit closely related to?
Maxillary
Frontal
Ethmoid
Which area of the orbit is the weakest?
Medial & inferior walls of the orbit
What cushions the eyeball in the orbit?
Periorbital fat
What is another name for the mucosa membrane on the inside of the eyelid?
Conjuntiva
What type of gland is associated with eyelashes?
Sebaceous gland
What muscle is responsible for elevating the eyelid?
Levator palpebrae superioris
What is the name of the hard plate found in the eye lid?
Tarsal plate
What is the name of the glands found in association with the tarsal plate in the eyelid which produce oily secretions?
Meibomian glands
What are the different areas of the conjuntiva called?
Palpebral conjunctiva
Ocular conjunctiva
Superior/ Inferior fornix
What does the ocular conjunctiva cover?
Sclera
Which nerve stimulates the lacrimal gland?
Facial nerve (parasympathetic)
Where do tears drain from the eyeball?
Via punctate in the medial side of eye into lacrimal sac
Where do tears drain from the lacrimal sac?
Nasolacrimal duct
Where does the nasolacrimal duct drain?
Inferior meatus
What do intrinsic muscles of the eye control?
Pupil diameter & regulate lens curvature
What do extra ocular muscles control?
The movement of the eyeball
What muscle constricts the iris? What innervation?
Constrictor pupillae (circular) Parasympathetic - IIIn
What muscle dilates the iris? What innervation?
Dilator pupillae (radial) Sympathetic nerves
What innervates the ciliary body muscles?
Parasympathetic (IIIn)
When the ciliary bodies are activated what happens to the structure of the lens? What is this called?
Thicker & rounded
Focus close up
Accomodatio
How many straight muscle (recti) are found in the eye orbit?
4 - SR, LR, MR, IR
How many oblique muscles are there?
2 - SO, IO
Where do the recti muscles arise/insert?
Apex of orbit from annular fibrous ring & insert anteriorly to sclera
Where does the SO arise/insert?
Roof of orbit & insert posteriorly to sclera
Where does the IO arise/insert?
Floor of orbit anteriorly & insert posteriorly
What nerve supplies the LR?
Abducent nerve (VI)
What nerve supplies the SO?
Trochlear nerve (IV)
What nerve supplies the IO
Oculomotor nerve (III)
Where do parasympathetic fibres carried by IIIn synapse?
Ciliary ganglion
Which nerve carries sensory information to the orbit?
Trigeminal nerve (V1 & 2)
Where dos the maxillary division of trigeminal exit onto the face?
Infraorbital foramen
What is the ophthalmic artery a branch of?
ICA
What branch of the ophthalmic artery travels within the optic nerve?
Central retinal artery
What is another name for the physiological blind spot?
Optic disc
What is the name of the area of retina which has a high density of cones?
Fovea centralis
What are the 4 divisions the retina is divided into?
Superonasal
Superotemporal
Inferonasal
Inferotemporal
Where do the superior & inferior ophthalmic veins drain into?
Cavernous sinus
Which germ layer do eyes originate?
Ectoderm (from neural tube)
Where do optic vesicles grow out from?
Diencephalic part of neural tube
What forms after the optic vesicle in embryonic development of eye?
Optic cup
What embryological layer forms the EOM?
Mesenchyme (mesoderm)
What epithelial layer is found at the cornea?
Stratified squamous non-keratinised epithelium
What is another name for the basement membrane at the corneal epithelium?
Bowman’s membrane
What is the thickest layer in the cornea called?
Stroma
What is the stroma of the cornea composed of?
Regularly arranged collagen
How many histological layers are present at the cornea?
5
What factors contribute to the cornea being transparent?
Regularly arranged collagen fibres in stroma
No blood vessles
Endothelial layer has pump which keeps AH out
Why does the avascularity of the cornea contribute to effective corneal transplants?
Less risk of rejection
How many layers compose the retina?
10 layers
What is the 1st layer of the retina composed of?
Pigmented epithelium
What is the 2nd retinal layer composed of?
Rods & cones
What is lens opacification called?
Cataract
What are the functions of the tear film?
Keeps cornea moist
Washes away particles of foreign body
Has antibodies
Smooths outer layer of cornea for refraction
Clinically how can you visualise the tear film?
Staining with fluorescein
How many layers compose the tear film?
3
1: mucinous layer
2: aqueous layer
3: oily layer
Which muscles elevate/depress the eye when it is adducted?
Oblique muscles
Which muscles elevate/depress the eye when it is abducted?
SR/IR
What is the mnemonic used to remember EOM movements?
RADSIN
Recti adductors
Superior intortors
What are the actions of the SR?
Elevation
Adduction
Intorsion
What are the actions of the IR?
Depression
Adduction
Extorsion
What are the actions of the SO?
Depression
Abduction
Intorsion
What are the actions of the IO?
Elevation
Extorsion
Abduction
What is the clinical term for squint?
Strabismus
What is the name of a convergent squint?
Esotropia
What is the name of a divergent squint?
Exotropia
What is amblyopia?
A lazy eye caused as a result of squint left uncorrected leading to suppression of image
What are the functional consequences of a squint?
Amblyopia
Diplopia
When there is an increase in illumination, what happens to the pupil?
Constricts via IIIn parasympathetic fibres
When there is an decrease in illumination, what happens to the pupil?
Dilates via sympathetic innnervation
In a pupillary reflex, what are the names of the responses you are looking for?
Direct
Consensual
What is the term used to describe pupils of different sizes? In what condition is this seen?
Anisocoria
eg Horners syndrome
In the pupillary reflex, does light go to the LGB & visual cortex?
No, it goes to the midbrain to the Edinger-Westphall nucleus (part of IIIn nucleus)
In the pupillary reflex, where do afferent fibres go from the EWN?
Preganglionic fibres pass through orbit via IIIn & synapse in ciliary ganglion.
Postganglionic fibres inveiate constrictor pupillae = PUPIL CONSTRICTION
What eye related condition is associated with MS?
Optic neuritis
What type of conditions can impair pupillary reflex?
Intracranial bleed
What disease can cause damage to IIIn however parasympathetic fibres are spared?
Diabetes
What are the clinical signs of Horners syndrome?
Anhydrosis
Ptosis
Miosis
Where do postganglionic sympathetic fibres travel?
Along blood vessels
Name a cause of Horners syndrome & what is its pathology
Loss of sympathetic innervation to the head
Tumour
Trauma
Pancoast lung tumour
What components of the eye are responsible for bending light?
Cornea
Lens
What is another term for the bending of light?
Refraction
When an object is close up, what happens to the shape of the lens? Why?
Lens becomes thicker
Light has to bend further in order to focus on retina
What part of the eye is the most powerful bender of light?
Cornea
The focusing capacity of the eye changes from distant to close object, is called?
Accomodation
What are the 3 changes occur when the eye accommodates?
Lens becomes thicker & spherical
Pupil constricts
Eyes converge
When the ciliary muscles contract, what happens to the lens?
Thicker & spherical
suspensory ligaments become lax
What innervation causes contraction of ciliary muscles?
Parasympathetic (IIIn)
What EOM do we use in order to converge eyes in accomdation?
MR
What is the clinical term for shortsightedness?
Myopia
In myopia, where does the light refract?
In front of the retina
If someone has myopia, what is there vision like?
Hazy in distance
Clear close up
If someone has emmetropia, what is there vision like?
Normal
What are some of the symptoms of myopia?
Headaches, unable to see blackboard
In infants = divergent squint
How can myopia be treated?
Reduce the bending power of lens by:
Spectacles
Contact lens
Laser eye surgery
What is the clinical term for farsightedness?
Hyperopia
If someone has hyperopia, what is there vision like?
Hazy close up
Distant is clear
Why might someone suffer from hyperopia?
Eyeball too short
Lens too flat
Where is the image formed in the eye in hyperopia?
Behind the retina
What are some of the symptoms associated with hyperopia?
Eyestrain after reading
Convergent squint
What can you use to treat hyperopia?
Contact lens
Laser eye surgery
Glasses
Where is the light focussed when a person has astigmatismsm?
Will not be refracted into one area on retina
Describe the pathology of astigmatisms
Les appears oval shaped resulting in light being bent differently
What will someones vision with astigmatism be like?
Hazy for close & distant vision
Ho can you treat astigmatism?
Laser eye surgery
Special spectacles - cylindrical glasses
Contact lens - topic lenses
What is longsightedness in older age called?
Presbyopia
Why does presbyopia occur in older age?
Lens becomes less mobile therefore when ciliary muscles contract, lens less able to change shape
How can presbyopia be treated?
Reading glasses
Where are photoreceptors found?
Retina
Define phototransduction
Defined as a conversion of light energy to electrochemical response by photoreceptors
Which vitamin is associated with phototransduction? What is its role?
Vitamin A (retinol) Visual pigment regeneration
What are the 2 types of photoreceptor found in the retina?
Rods & cones
What is the main visual pigment found in the eye?
Rhodopsin
What is the main source of vitamin A?
Diet
If there is vitamin A deficiency, what will be clinical signs?
Night blindness
In what conditions can vitamin A dificiency occur?
Malabsorption disease - coeliac disease
What are some clinical signs of vitamin A defiency observed in the eye?
Bitots spots in conjunctiva
Corneal ulceration
Opacification of cornea (silver spots)
What is the visual field defined as?
Everything you can see in ONE eye (including periphery)
Where is maximal visual acuity achieved?
Fovea centralis
What is absent at the optic nerve head?
Rods & cones
Which fibres cross at the optic chiasm?
Nasal fibres
Where do fibres from optic tract synapse?
LGB
Where is the LGB found?
Thalamus
In the visual cortex, which visual field does the left side of the brain perceive?
Right visual field
If the optic tract or optic radiation is damaged, what will happen to visual field?
Contralateral homonymous hemianopia
If there is damage to the optic chiasm, what will happen to the visual field?
Bitemporal hemianopia