objective 9 Flashcards
protect the eye from injury.
eyelids
larger and more mobile
upper eyelids
filter out dust and dirt
eyelashes
elliptical open space between the eyelids
palpebral fissure
the eyelids margins approximate completely
when the eyes are closed
the upper eyelid covers part of the iris. the lower eyelid margin is just at the limbus
when the eyes are open
boarder between the cornea and sclera
limbus
the corner of the eye, angle where the eyelids meet
canthus
a small fleshy mass that contains sebaceous glands
caruncle
strips of connective tissue that give the eyelid shape. they are located in the upper eyelid
tarsal plates
contained in the tarsal plates, they secrete an oily lubricating material onto eyelids
meibomian glands
transparent protective covering on the exposed part of the eye
conjunctiva
provides constant irrigation to keep the conjunctiva and cornea moist and lubricated
lacrimal apparatus
where the tears drain into
puncta
how many eye muscles are there?
6
tough protective white covering that is continuous anteriorly with the cornera
outer fibrous sclera
transparent and covers iris and pupil
cornea
has dark pigmentation to prevent light from reflecting
internally and is heavily vascularized to deliver blood to the retina
choroid
controls the amount of light admitted into the retina
iris
size determined by a balance of the parasympathetic and sympathetic chains of the autonomic nervous system
pupil
serves as a refracting medium, keeps a viewed object in constant focus on retina
lens
contains fluid that continuously flows
anterior chamber and posterior chambers
visual receptor of the eye which light waves are changed into nerve impulses
retina
area in which fibers from the retina converge to form the optic nerve
optic disc
include paired artery and vein extending to each quadrant
retinal vessels
recieves and transduces light from the center of the visual field
macula
area of sharpest and keenest vision
fovea centralis
Light rays are refracted through the
cornea, aqueous humor, lens, and vitreous body, the light rays strike
the retina
* Retina transforms light stimulus to nerve impulses
* Nerve impulses are conducted via the optic nerve and the optic tract
to the visual cortex of the occipital lobe
visual pathways and fields
normal constriction of the pupils
when a bright light shines on the retina
pupillary light reflex
when one eye is exposed to bright light, constriction of that pupil occurs
direct light reflex
when one eye is exposed to bright light, the other pupil constricts at the same time
consensual light reflex
reflex direction of the eye toward an object attracting a persons attention
fixation
adaptation of the eye for near vision
accomodation
what are the eyes like at birth?
Eye function limited, matures fully during early years (Eyeball
reaches adult size by 8 years)
* Peripheral vision intact
* Poorly coordinated eye movements (binocularity by 3-4
months)
* Macula absent (begins developing by 4 months and is mature
at 8 months)
* Iris has little pigmentation, the pupils are small, the lens is
nearly spherical
* Most neonates born farsighted (80%)
Difficult to perform on an infant - only check the red reflex
* Young children and school-age children - examination same as
for adults
* When testing visual acuity, screening method chosen
depends on the age of the child (p. 333 - 334)
* Testing for strabismus is an important screening
measure during early childhood
funduscopic examination
no effect on vision
arcus senilis