vision 1 and 2 Flashcards
3 layers of the eyeball
outer tunic
middle tunic
inner tunic
outer tunic
-consists of cornea and sclera
-is fibrous
middle tunic
-consists of choroid, ciliary body and iris
- is vascular and pigmented
inner tunic
- consists of the retina
- is neurosensory
cornea function
to refract light
- curvature of anterior corneal surface
- tear film
- corneal thickness
to transmit light
- regularly arranged epithelium
-absence of blood vessels
sclera function
provides rigidity
- to allow insertion of extra ocular muscles
- to maintain shape of eyeball
- opaque
- makes up the bulk of the outer coat
cornea epithelium
Stratified squamous mEpithelium
-because it’s in contact with the external environment. So cells are always sloughing off and being damaged.
- cells in this bottom layer of the epithelium will produce new cells which will migrate to the top to keep that barrier intact.
-These cells are stuck together very tightly.
cornea - Bowmans layer
- Acellular - no cells
- Made up of collagen fibres
- People who have had this layer removed don’t seem to have any functional loss to vision
Maybe provide rigidity but not sure
cornea - stroma
- Thick layer - connective tissue
- Collagen fibres are arranged parallel to one another
○ Makes the cornea transparent
cornea - descemet’s membrane
another layer of collagen fibrils
cornea - endothelium
- Cuboidal cells
- the endothelium is in contact with the aqueous humor.
- it’s going to help transport substances into the cornea Like Oxygen and help get rid of waste products from the cornea into the aqueous humor.
sclera fascial sheath
connective tissue - eyeball is supported by it
sclera - episclera layer
tough - connective tissue - lots of collagen fibres
sclera - stroma
the same as the cornea except that the collagen fibers and randomly arranged and because the randomly arranged and not arranged in a parallel fashion, The stroma is not transparent
sclera - lamina fusca
Connective tissue
sclera - choroid
Part of middle layer of eye
avascular cornea
- cornea has no blood supply
- it is avascular and transparent
- it receives nutrients from the aqueous humour and tear film - Oxygen dissolves inti the tear film and then into the cornea
anterior scleral perforations
- anterior ciliary vessels
- recti muscles
posterior scleral perforations
- optic nerve
- central retinal vessels
- ciliary nerves and vessels
central scleral perforations
- vortex veins
lamina cribrosa
- the weakest part of the sclera
- surrounds optic nerve
middle tunic - ciliary body
- plays a key role in accommodation
- produces and secretes aqueous humour
- suspends the lens
middle tunic - choroid
- vascular pigmented layer
- allows passage of blood vessels and nerves to anterior segment
- prevents unwanted reflection of light - has some melanin pigment in it
choroid: histology
long and short posterior ciliary arteries, anterior ciliary arteries, vortex veins
choroid stroma
blood vessels, connective tissue and melanocytes
choroid - Bruchs membrane
multilayered sheet with elastic core
Allows passageway of substances into and out of the choroid
ciliary body - ciliary muscle
- 3 sets of smooth muscle fibres
These muscle fibres help with accomodation
ciliary body - ciliary stroma
vascular connective tissue
goes into these finger-like processes called ciliary processes.
this whole region where you have ciliary processes is called Pars plicata
So the ciliary stroma goes into each one of these ciliary processes and each one
of the ciliary processes is lined by a double layer of ciliary epithelium
ciliary body - ciliary epithelium
- double layer
- outer pigmented
- inner non-pigmented
- produces and secretes aqueous humour
what happens when you look at something close to your face
when you look at something close to my face, my ciliary body will be contracting and when it contracts it moves in this direction towards the lens.
if the ciliary body is moving towards the lens the suspensory ligaments become really Slack and then the lens can become nice and fat.
what happens when you look at something far away
when you look at something far away ciliary body relaxes.
- It falls back, the suspensory ligaments become taught and then the lens becomes nice and thick.
So it’s the ciliary muscle that helps to carry out that accommodation.
what is the iris made up of
it’s made up of stroma Anteriorly and a double-layered epithelium posteriorly
what does the iris control
the iris controls the amount of light that enters the eye - it has to dilate and constrict.
how does the iris control the amount of light that enters the eye
it does through these muscles - the sphincter papilae is embedded within the stroma and it causes miosis - causes pupil to constrict
the opposite muscle is called dilator pupillae and it is part of this epithelial layer.
○ Dilate the pupil - Mydriasis
what is the epithelium in the iris closest to the stroma called
myoepithelium
when do miosis and mydriasis happen in the iris
miosis - Happens when the parasympathetic nervous system is activated
mydriasis - Happens when sympathetic nervous system is activated
trabeculae - iris
Radiate from the pupil to the periphery of the iris
These are columns of collagen that radiates out.
iris - collarette
- Where the iris is quite thick
- Divides the iris into 2 zones
○ Ciliary zone - most outer bit
○ Pupillary zone
- Divides the iris into 2 zones
iris - flush’s crypts
the aqueous humour can enter and
exit the Flushs’ of the iris.
inner tunic - the retina
site of transformation of light energy into a neural signal
it extends from the optic nerve posteriorly anteriorly to where the ciliary body is
the retina - retinal pigmented epithelium
- main job is to again absorb excess light so you don’t get such unwanted reflection.
another one of their main jobs is to make sure that these photoreceptors - rods and cones Work well
photoreceptors in the retina
Full of photopigment - every time light hits your eyes these photopigments change shape And then the rod and the cones gets rid of them from this end. So these photo pigments are then all just discarded.
bipolar cells - retina
- Neurons
- Synapse with photoreceptors at one end and synapse with ganglion cells at other end
-2 poles
retina - horizontal cells
- They’re found at the interface between the photoreceptors and the bipolar cells.
amacrine cells - retina
found at the interface between the bipolar and the ganglion cells
ganglion - retina
Multipolar neurones
- Its the axons of these ganglion cells that form the optic nerve
retinal layers
ganglion cell layer
- inner plexiform layer
- inner nuclear layer
- outer plexiform layer
- outer nuclear layer
- layers of rods and cones
outer plexiform layer of the retina
Outer plexiform layer is where you find the processes of the rods and
cones.
inner nuclear layer of the retina
Inner nuclear layer - horizontal bipolar and amacrine nuclei make up the inner nuclear layer.
inner plexiform layer
Inner plexiform layer - axons of horizontal, bipolar and amacrine cells
outer nuclear layer- retina
Nuclei of rods and cones found in outer nuclear layer
ganglion cell layer - retina
Ganglion cell layer - where the cell bodies lie
retinal neurones - bipolar cells
- 1st order neurones of the visual pathway
- relay information from photoreceptors to ganglion cells
- many different types
ganglion cells
- 2nd order neurones of the visual pathway
-exit retina at the optic disc - axons form the optic nerve
- optic nerve exits eyeball at lamina cribrosa
- many different cell types
amacrine cells
horizontal transfer of information
- modulates information reaching ganglion cells
- many different types
horizontal cells
horizontal transfer of information
- able to effect inhibitory response
- several different types
retinal pigmented epithelium
- protective (forms part of blood retina barrier)
- phagocytoses fragments from photoreceptor outer layer
- metabolises and stores vitamin A
- produces growth factors
- pigments help to decrease excess scattering of light
optic disc of retina
optic disc. That’s where all your ganglion cell
Are going to leave the retina.
fovea centralis - retina
where highest concentration of cones are found
aqueous humour
- supplies metabolic needs of the lens and cornea
- contains water, glucose, proteins, dissolved gasses and other nutrients
- supports wall of eyeball and helps maintain its shape
vitreous humour
- helps maintain shape of eyeball
- contains proteins, salts, acids, hyalocytes and 98% water
- transmits light
- contributes to the dioptric power of eye
- supports lens
- supports retinal layers
segments of the eye
anterior segment
- anterior to the lens
posterior segment
- everything posterior to the lens
chambers of the eyeball
anterior chamber - 0.2 ml
posterior chamber - 0.06 ml
canal of Schlemm
aqueous humour goes through the trabecular meshwork before entering the canal of Schlemm
it is drained by 25-35 collector channels which eventually empty into anterior ciliary veins
rate of formation of aqueous humour is 1-2 microl/minute
aqueous humour normal intraocular pressure
10-20 mmHg
determined by:
- rate of formation of aqueous humour
- rate of drainage through trabecular meshwork
- pressure in the episcleral veins
glaucoma
poor drainage through the meshwork can cause increased intraocular pressure
this can lead to optic nerve atrophy and defects in the visual field
peripheral fields are lost first in glaucoma
