vision Flashcards
eye anatomy: identify the optical and functional anatomical components of the eye
diagram of the bony orbit
slide 3; made of 3 bones with several holes at back for nerves and blood supply; fractures when hit by non-sharp object (sclera protects eye as very hard)
3 types of tear production
basal, reflex (irritation), crying (emotional)
reflex tears: afferent innervation
cornea, V1 (opthalmic division of trigeminal)
reflex tears: efferent NS
PSNS
reflex tears: neurotransmitter
ACh
what produces tears
lacrimal gland
movement pathway of tears
lacrimal gland -> drains through two puncta opening on medial lid margin -> flows through superior and inferior canaliculi -> gather in tear sac -> exit through tear duct into nose cavity
diagram of lacrimal system
slide 4
what does tear film maintain
smooth cornea-air surface
3 functions of tear film
oxygen supply to cornea (no blood vessels), removal of debris (including blinking), bactericide
3 layers of tear film (external to internal)
superficial oily layer, aqueous tear film, mucinous layer
function of superficial oily layer of tear film
reduce tear film evaporation (produced by row of Meibomian glands along lid margins)
what is present in aqueous tear film
tear gland
function of mucinous layer
on corneal surface to maintain surface wetting
what is conjunctiva
thin, transparent tissue covering outer surface of eye
location of conjunctiva
begins at outer edge of cornea, covering visible part of eye, and lines inside of eyelids; prevents anything entering behind eye (acts as a sac)
what supplies conjunctiva with nutrients, and when are they visible
tiny blood vessels; visible in conjunctivitis
diagram of eye
slide 6
3 layers of coat of eye (outer to inner)
sclera, choroid, retina
3 features of sclera
hard, high water content, opaque (white of eye)
features of choroid
pigmented, vascular
retina type of tissue
neurosensory
function of sclera
protective outer coat
what is continuous with sclera anteriorly
cornea
what is the cornea
transparent, dome-shaped window covering front of eye
main function of cornea
powerful refracting surface, providing 2/3 of focusing power (convex; higher refractive index than air)
water content of cornea
low
2 other functions of cornea
physical barrier, infection barrier
5 layers of cornea (outer to inner)
epithelium, Bowman’s membrane, stroma (thick), Descemet’s membrane, endothelium
how does stroma organisation affect transparency
regular structure increases transparency
what provides nutrients and sensation in stroma
corneal nerve endings
function of endothelium
pumps fluid out of cornea, preventing corneal oedema
suscpetibility and consequence of endothelium dysfunction
only 1 layer and no regeneration power, with cell density decreasing with age, so dysfunction may result in corneal oedema and cloduiness
outcome of hydrating cornea
becomes white
what is the uvea
vascular coat of eye ball, lying between sclera and retina
3 parts of uvea (from front to back); significance of being very close)
iris, ciliary body, choroid; disease of one part also affects other portions (not necessarily to same degree)
location and function of choroid (posterior part of uvea)
between retina and sclera; composed of layers of blood vessels that nourish back of eye
function of iris
coloured part which controls light levels inside eye (embedded with small muscles that dilate or constrict pupil)
name of round opening in iris centre
pupil
location of lens
outer acellular capsule
structure of lens
regular inner elongated cell collagen fibres, which contribute to transparency
name of lens loss of transparency
cataract
3 functions of lens
transparency, refractive power (1/3), accomodation (as elastic)
what is lens suspended by which causes it to change shape and consequently focus
lens zonules (fibrous ring) which consists of passive connective tissue; when contract, push towards themselves, allowing lens to contract
diagram of how lens focuses light
slide 12; image upside down
what is the retina and where is it
very thin layer of tissue that lines inner part of eye
function of retina
capture light rays, which then are sent as impulses to brain via optic nerve
where does optic nerve connect
back of eye near macula
what is the visible portion of optic nerve calles
optic disc (most obvious structure; blood vessels become thinner the further forward from optic disc)
where is the macula located
centre of retina, temporal to optic nerve
what is the macula
small, highly sensitive part of retina (1:1 photoreceptor to neurone ratio)
function of macula
detailed central vision (appreciate detail, read etc.)
what is the very centre of the macula
fovea
section of eye in between upper and lower eyelids
palpebral fissure
name of corners of eye
lateral and medial canthus
name of white part of eye
sclera
name of section inside medial canthus (pink structure)
caruncle
name of dark ring acting as border between cornea and sclera
limbus
what fills the eye and keeps it in shape
vitreous humour
