Jarvis Chapter 14 Eyes Flashcards
eyelids
two movableshades that further protect the eye from injury, strong light, and dust
palpebral fissure
the elliptical open space between the eyelids
limbus
the border between the cornea and the sclera
canthus
the corner of the eye, the angle where the lids meet.
caruncle
found in the medial canthus, it is a small fleshy mass containing sebacceous glands
tarsal plates
found within the upper lid, these strips of connective tissue that give it shape. contain meibomian glands
meibomian glands
modified sebacceous glands that secrete an oily lubricating material onto the lids. this stops tears from overflowing and helps to form an airtight seal when the eyelids are closed. conatined by the tarsal plates
conjunctiva
the transparent protective covering over the exposed part of the eye. a thin mucus membrane folded like an envelop between the eyelids and eyeball.
palpebral conjunctiva
the thin mucous membrane that specifically lines the lids and is clear with many small blood vessels
bulbar conjunctivea
a thin mucous membrane that overlayes the eyeball, with the white sclera showing through. at the limbus the conjunctiva merges with the cornea
lacrimal apparatus
the provider of constant irrigation to keep the conjunctiva and cornea moist and lubricated. lacrimal gland, puncta, nasolacrimal sac, nasolacrimal duct, inferior meatus
rectus
the extraocular muscles that are straight. there are four muscles: superior, inferior, lateral, and medial
oblique
the two extraocular muscles that provide rotary movement: superior and inferior
Cranial Nerve VI
the abducens nerve which innervates the lateral rectus muscle (abducts the eye)
Cranial Nerve IV
the trochlear nerve which innervates the superior oblique muscle
Cranial Nerve III
the oculomotor nerve. innervates all the rext (superior, ingerior and medial rectus and the inferior oblique muscles
sclera
the outer fibrous layer of the eye. a tough, protective white covering
choroid
the middle vascular layer of the eye which has dark pigmentation to prevent light from reflecting internally and is heavily vascularized to deliver blood to the retina. this layer is ontinuous with the ciliary body (control the thickness of the lens) and the iris (functions as a diaphragm, varying the opening at its center and controls the amount of light admitted into the retina
retina
the inner nervous layer of the eye. This visual receptive layer of the eye changes light waves into nerve impulses. these impulses are conducted through the optic nerve and the optic tract to the cisual cortex of the occipital lobe. the image formed on this area of the eye is upside down and inversed form its actual appearance in the outside world.
cornea
continuous anteriorly with the sclera, which covers the iris and the pupil. it is part of the refracting media of the eye, bending incoming light rays so they will be focused on the inner retina. this is very sensitive to touch, contact with anything will stimulate a blink in both eyes
pupil
round and regular. its size is determined by a balance between the para/sympathetic chains of the autonomic nervous system
lens
a biconvex disc located just posterior to the pupil. serves as a refracting medium keeping a viewed object in continual focus on the retina
anterior chamber
posterior to the cornea and in front of the iris and lens. contains aqueous humor that is produced continually by the ciliary body. this continual flow of fluid serves to deliver nutrients to the surrounding tissues to drain metabolic wastes
optic disc
the area in which fibers from the retina converge to form the optic nerve
retinal vessels
vessels of the retina which normally include a paired artery and extend to each quadrant, growing progressively smaller in caliber as they reach the periphery
fovea centralis
the area of the retina which has the sharpest and keenest vision.
macula
a slightly darker pigmented region surrounding the fovea centralis. this receives and transduces light from the center of the visual field.
transparent media
the cornea, aqueous humor, lens, and vitreous body
pupillary light reflex
the normal constriction of the pupils when bright light shines on the retina. the afferent link is CN II, the optic nerve, and the efferent path is CN III, the oculomotor nerve. In order to test this reflex, darken the room, ask the person to gaze into the distance, and advance a light from the side and note response. A constriction of the same-sided pupil is a direct light reflex, and a simultaneous constriction of the other pupil is a consensual light reflex.
fixation
a reglex direction of the eye toward an object attracting a person’s attention. the image is fixed int he center of the visual field, the fovea centralis. this consists of very rapid ocular movements to put the target back on the fovea centralis
accomodation
an adaptation of the eye for near vision by increasing the curvature of the lens through movement of the ciliary muscles. test this reflex by asking the person to focus on a distant object, which dilates the pupils, then have them shift gaze to a close object. A normal response is papillary constriction and convergence of the axes of the eyes.
presbyopia
a condition found in aging adults where the pupil size decreases, the lens loses its elasticity and becomes hard and glasslike. this decreases the lens’ ability to change shape in order to accomodate for near vision. average age of onset is 40
Snellen Alphabet chart
the most commonly used and accurate measure of visual accuity. it contains lines of letters in decreasing size. have the person sand 20’ away. the top number indicates the distance the person is standing from the chart, while the denominator gives the distance at which a normal eye could have read that particular line
confrontation test
a gross measure of peripheral vision
corneal light reflex
assess the parallel alignment of the eye axes by shining a light toward the person’s eyes. direct the person to stare straight ahead as you hold the light about 12 inches away. note the reflection of the light on the corneas, it shoudl be in exactly the same spot on each eye
cover test
a test that detects a small degree of deviated alignment by interrupting the fusion reflex that normally keeps the two eyes parallel. ask the person to stare straight ahead at your nose, place a card in front of one eye and note the uncovered eye. A normal response is a steady fixed gaze.. if the uncovered eye jumps to reestablish fixation, eye muscle weakness exists
diagnostic positions test
lead the eyes through the six cardinal positions of gaze will elicit any muscle weakness during movement. ask person to hold head steady and follow finger. progress clockwise in each direction. a normal response is parallel tracking of the object with both eyes
nystagumus
a fine oscillating movement best seen around the iris.
exophthalmos
protruding eyes
ophthalmos
sunken eyes
opacities
cloudiness of the cornea and lens
arcus senilis
a gray-white arc or circle around the limbu; it is due to the deposition of lipid material in the aging adult. as lipids accumulate, the cornea may look thickened and raised. but this has no effect on vision
anisocoria
an unusual sample of people who have pupils of two differentsizes
PERRLA
pupils equal, round, react to light and accomodation
media
the anterior chamber, lens, and vitreous of the eye which can be viewed by the ophthalmoscope
ocular fundus
the internal surface of the retina that can be seen by the ophthalmoscope.
diopter
the unit of strength of each lens in the ophthalmoscope. positive, black nurmbers indicate objects nearer in space to the ophthalmoscope, and the red, negative numbers are for focusing on objects farther away.
red reflex
the red glow filling the person’s pupil which is caused by the reflection of your ophthalmoscope light iff the inner retina. use the red lenses for nearsighted eyes and the black for farsighted eyes.
scleral crescent
a gray-white new moon shape aournd the disc margins which occurs when pigment is absent in the choroid layer and you are looking directly at the sclera
pigment crescent
black around the disc margins because of accumulation of pigment in the choroid.
strabismus
squint, crossed eye. Causes disconjugate vision because one eye deviates off the fixation point
corneal light reflex
shine a light toward a child’s eye. the light should be reflected in the same spot in the two corneas.
epicanthal fold
an excess skinfold extending over the inner corner of the eye. partly or totally overlapping the inner canthus. in non-Asian children it isappears as the child frows.
pseudostrabismus
the appearance of malallignment due to the presence of epicanthal folds. yet the corneal reflex is normal
pinguecullae
shown on the sclera, these yellowish elevated nodules are due to a thickening of the bulbar conjunctiva from prolonged exposure to the sun, wind, and dust.
xanthelasma
soft, raised yellow plaques occuring on the lids at the inner canthus
drusen
a normal development in aging adulys which consists of benign degenerative hyaline deposits. these small, round, yellow dots are scattered haphazardly on the retina. they are scattered in no pattern, but they usually are symmetrically placed in the two eyes. they have no effect on vision
strabismus
eyes are not properly alligned with each other
esotropia
one or both eyes turn inward
Hischberg test
a simple screening test for strabismus, is performed by shining a light and noting the reflection of the light on the eye of the person. if it is the reflection is in the same spot of both people, their eyes are aliigned with each other
visual acuity
recorded as a fraction. the numerator is the distance from the chart and the denominator represents the last line read correctly
