Visual System Flashcards
when are tears produced by the lacrimal gland?
basal, reflex and emotional responses
what is the control of a tear reflex ie a bug lands on eye
afferent - CN V1 opthalmic trigeminal
efferent - parasympathetic
acetylcholine neurotransmitter
what is the route of a tear from lacrimal gland to nasal cavity?
lacrimal gland - drain through two puncta
flow through superior and inferior canaliculi
gather in tear sac
exit through tear duct into nasal cavity
what is the tear film?
most superficial layer of eye - maintains a smooth cornea-air surface
supplies oxygen to cornea
what is the role of the tear film?
supplies oxygen to cornea
bactericidal
removes debris and dust
what are the 3 layers of the tear film?
lipid outer layer, aqueous layer, mucinous layer on cornea surface
what is the conjunctiva?
thin, transparent tissue covering outer surface of the eye
lines eyelids and visible part of the eye
what are the 3 tissue layers of the eyeball?
sclera
choroid
retina
what is the sclera?
the white of the eye
tough, opaque outer coat
high water content
what is the cornea?
transparent, dome shaped window covering front of eye
low water content
provides 2/3 of focusing power
what are the layers of the cornea?
epithelium bowmans membrane stroma descemets membrane endothelium - pumps fluid out of cornea to prevent oedema
what is the uvea?
choroid, iris and ciliary body
most vascular part of the eye
what is the choroid?
lies between retina and sclera
layers of blood vessels
what is the iris?
muscular to dilate and constrict the pupil size
controls light levels inside the eye
what is the structure of the lens?
outer acellular capsule
regular inner elongated cell fibres
what is the function of the lens?
transparency
refractive power and 1/3 of focusing power
accomodation
elasticity
what is the retina?
thin layer of tissue lining the inner eye
captures light rays and send to optic nerve
what is the optic disk?
visible portion of the optic nerve
what is the blind spot and why does it occur?
where the optic nerve meets the retina
there are no light sensitive cells
where does the optic nerve join the eye?
back of the eye, near the macula
what is the macula?
the centre of the retina highly sensitive for detailed central vision
what is the centre of the macula called?
fovea
what is the role of the fovea?
appreciates detail and focuses central vision
what is central vision?
detail day/colour vision
reading, facial recognition
by fovea of macula