The Eye Flashcards
What is refraction
bending of light due to difference in speed through different media
How does light travel
straight lines
How can light be manipulated
reflected, absorbed and refracted
What is the cornea important for
refraction
What is the function of the sclera
protection and maintenance of shape
What is the function of extra ocular muscles
move the eyeball
What controls the extra-ocular muscles
occulomotor nerve
Describe the optic disk
where blood vessels and nerves come into the eye
What is the function of the optic nerve
carries axons from the retina to the brain
Describe the macula
region of retina, devoid of large blood vessels
What is the function of the macula
central vision , quality of vision
Describe the fovea
thin, area of highest visual acuity
Where is the fovea located
macula
What does the fovea contain
photoreceptors
What is the aqueous humour
watery fluid
What is the function of the aqueous humour
provide nutrients to cornea and lens
When is the vitreous humour formed
embryonic development
Function of the canal of schlemm
drain the aqueous humour
What is the vitreous humour
viscous fluid - jelly like
What is the function of the vitreous humour
keeps the eyeball spherical, pushes retina down, provides clearer images
Name two diseases of the eye
cataracts, glaucoma
What is attached to the lens
zonal fibres
What is the function of zonal fibres
enable stretching of the lens
Describe cataracts
clouding of the lens
Why does cataracts occur
changes in composition of the aqueous humour
What causes glaucoma?
slowed uptake of aqueous humour
What are the symptoms of glaucoma
elevated intraocular pressure, compression of the optic nerve, reduced BS to retina
Why does light move slower through the retina
increased density
What determines degree of refraction
difference between two media
How much refraction is needed for straight light rays
less
Describe the lens when looking at distant objects
flattened, weak
Describe the lens when looking at closer objects
rounded, strong
Descirbe the ciliary muscle when looking on distant objects
relaxed
What is the effect of rounding the lens
increases refractive power to focus closer objects
Name some problems with focusing
hyperopia, myopia, presbyopia
Describe hyperopia
far sightedness, not enough refraction
How is hyperopia corrected
convex lens - increases refraction
Describe myopia
short sightedness, long eyeball, more refraction
What is presbyopia
loss of accommodation with ages - affects lens
What regulates light levels
iris
What constricts pupils
smooth circular msucle
What dilates pupils
smooth radial muscle
What innervates the muscles of the pupil
autonomic nervous system
Which muscles in the eye does the parasympathetic nervous system innervate
inner circular muscles
What is the effect of parasympathetic NS on the pupil
constriction
What muscles of the eye does the sympathetic NS innervate
outer radial muscles
What is the function of the pupillary light reflex
enables us to adjust to changes in light intensity
