Visual System - Anatomy Flashcards
Label an image of an eye.
Must include: pupil, iris, sclera, medial/lateral canthus, caruncle, limbus, eyelids, palpebral fissure,
List types of tears.
basal
reflex
emotional
Describe afferent innervation to the lacrimal system.
cornea, cranial nerve V1 – ophthalmic trigeminal
Describe efferent innervation to the lacrimal system.
parasympathetic
What neurotransmitter involved in the lacrimal system?
acetylcholine
Where are tears produced?
lacrimal gland
Tears drain through what?
two puncta, openings on medial lid margin
Tears flow through (?) to gather in the (?).
superior/inferior canaliculi
tear sac
From the tear sac, tears exit through (?) into (?).
tear duct
nasal cavity
Function of the tear film?
Maintains smooth cornea-air surface
Oxygen supply to Cornea (no blood vessels)
debris removal
bactericide
The tear film is composed of how many layers? Name them from superficial to deep.
superficial lipid layer
aqueous tear film
mucinous layer
Superficial lipid layer is produced by?
Meibomian glands along lid margins
What is the conjuctiva?
Thin, transparent tissue that covers the outer surface of the eye
What does the conjuctiva cover?
It begins at the outer edge of the cornea, covers the visible part of the eye, and lines the inside of the eyelids
Is the conjuctiva vascularised?
yes
List the layers of the coat of the eye from superficial to deep.
sclera
choroid
retina
Describe the sclera.
hard & opaque
protective outer layer
high water content
Describe the choroid.
pigmented
vascular
Describe the retina.
neurosensory tissue
What is the cornea?
transparent, dome shaped window covering the front of the eye, low water content
What is the cornea’s function?
refracting surface
2/3 of eye’s focusing power
What are the 5 layers of the cornea?
epithelium Bowman's membrane stroma Descemet's membrane endothelium
Function of endothelium of cornea
pumps fluid out of corneal and prevents corneal oedema
What is uvea?
Vascular coat of eyeball and lies between the sclera and retina
The uvea is composed of?
iris
ciliary body
choroid
What is the purpose of the iris?
controls light levels inside the eye similar to aperture on a camera
Opening of the iris is the?
pupil
Structure of the lens?
Outer acellular capsule
Regular inner elongated cell fibres – transparency
When the lens loses transparency with age, it’s called?
cataracts
List functions of the lens.
Transparency Regular structure Refractive Power 1/3 of the eye focusing power - higher refractive index than aqueous fluid and vitreous Accommodation Elasticity
What is the retina responsible for?
capturing the light rays that enter the eye
Light impulses are sent to the brain from the retina via?
optic nerve
Where does the optic nerve reach the retina?
back of the eye near the macula, visible portion called optic disc
Where is the macula located?
roughly in the centre of the retina
What is the macula responsible for?
detailed central vision
What is the fovea?
centre of the macula
What are the concentration of rods and cones in the fovea?
highest conc of cones
lowest conc of rods
Describe central vision. How is it assessed?
Detail day vision, colour vision
Reading, facial recognition
Loss of foveal vision – Poor visual acuity
How is central vision assessed?
Assessed by visual acuity assessment
Describe peripheral vision.
Shape, movement, night Vision
Navigation vision
Extensive loss of visual field – unable to navigate in environment, patient may need white stick even with perfect visual acuity
How is peripheral vision assessed?
Assessed by visual field assessment
Describe the layers of the retina.
outer
middle
inner
Outer layer of the retina
photoreceptors
detection of light
Middle layer of the retina
bipolar cells
local signal processing (improves contrast sensitivity, regulate sensitivity)
Inner layer of the retina
retinal ganglion cells
transmission of signal from the eye to the brain
What are the two classes of photoreceptors?
rods
cones
Rods
longer outer segment with photo-sensitive pigment
100 times more sensitive to light than cones
Slow response to light
Responsible for night vision (Scotopic Vision)
120 million rods
Cones
Less sensitive to light, but faster response
Responsible for day light fine vision and colour vision (Photopic Vision)
6 million cones
S cones capture what colour?
blue
M cones capture what colour?
green
L cones capture what colour?
red
What is deuteranomaly/Daltonism?
most frequent form of colour blindness
Which colour are people with deuteranomaly unable to perceive?
red
What is the term used to describe full colour blindness?
achromatopsia
