ch 15 EYES Flashcards
two rapid window shades that further protect the eye from injury, strong light, and dust
eyelids
is the elliptical open space between the eyelids
palpebral fissure
the border between the cornea and sclera
limbus
is the corner of the eye, the angle where the lids meet
canthus
At the inner canthus is a small, fleshy mass containing sebaceous glands.
caruncle
are strips of connective tissue that give it shape
tarsal plates (upper eye lid)
tarsal plates contain the ?, modified sebaceous glands that secrete an oily lubricating material onto the lids. This stops the tears from overflowing and helps form an airtight seal when the lids are closed.
meibomian glands(upper eye lid)
exposed part of the eye has a transparent protective covering .
-thin mucous membrane folded like an envelope between the eyelids and the eyeball
conjunctiva
lines the lids and is clear, with many small blood vessels
palpebral conjunctiva
overlays the eyeball, with the white sclera showing through
bulbar conjunctiva
covers and protects the iris and pupil.
cornea
provides constant irrigation to keep the conjunctiva and cornea moist and lubricated
-secretes tears
lacrimal apparatus
tears wash across the eye and are drawn up evenly as the lid blinks drain into the ?, visible on the upper and lower lids at the inner canthus.
puncta
- Six muscles attach the eyeball to its orbit
- superior rectus, inferior rectus, lateral rectus, and medial rectus, superior oblique m, inferior oblique
- two slanting, or oblique, muscles are the superior and inferior muscles.
Extraocular Muscles
two eyes move, their axes always remain parallel
conjugate movement
are important because the human brain can tolerate seeing only one image
Parallel axes
animals can perceive two different pictures through each eye, humans have a
binocular, single-image visual system
is stimulated by three cranial nerves (CNs)
EOMs
abducens nerve (CN VI) innervates the lateral rectus muscle (which abducts the eye); the trochlear nerve (CN IV) innervates the superior oblique muscle; and the oculomotor nerve (CN III) innervates all the rest—the superior, inferior, and medial rectus and the inferior oblique muscles.
three cranial nerves (CNs)
only parts accessible to examination are the sclera anteriorly and the retina through the ophthalmoscope.
Internal eye
(1) the outer fibrous sclera,
(2) the middle vascular choroid, and
(3) the inner nervous retina (inside is transparent vitreous body)
asymmetric sphere composed of three concentric coats(internal eye)
is a tough, protective white covering. It is continuous anteriorly with the smooth, transparent cornea, which covers the iris and pupil
sclera (outer layer)
is part of the refracting media of the eye, bending incoming light rays to focus them on the inner retina.
-transparent, and very sensitive to touch; contact with a wisp of cotton stimulates a blink in both eyes, called the corneal reflex. The trigeminal nerve (CN V) carries the afferent sensation into the brain, and the facial nerve (CN VII) carries the efferent message that stimulates the blink.
cornea
has dark pigmentation to prevent light from reflecting internally and is heavily vascularized to deliver blood to the retina.
choroid
is round and regular. Its size is determined by a balance between the parasympathetic and sympathetic chains of the autonomic nervous system.
-Stimulation of the parasympathetic branch, through CN III, causes constriction of the pupil. Stimulation of the sympathetic branch dilates the pupil and elevates the eyelid
pupil
is a biconvex disc located just posterior to the pupil. The transparent lens serves as a refracting medium, keeping a viewed object in continual focus on the retina. Its thickness is controlled by the ciliary body;
lens
is posterior to the cornea and in front of the iris and lens.
–contain the clear, watery aqueous humor that is produced continually by the ciliary body.
anterior chamber
lies behind the iris to the sides of the lens.
-contain the clear, watery aqueous humor that is produced continually by the ciliary body.
posterior chamber
is the visual receptive layer of the eye in which light waves are changed into nerve impulses. It surrounds the soft, gelatinous vitreous body.
retina
is the visual receptive layer of the eye in which light waves are changed into nerve impulses. It surrounds the soft, gelatinous vitreous body.
retina (inner layer)
is the area in which fibers from the retina converge to form the optic nerve. Located toward the nasal side of the retina, it has these characteristics: a color that varies from creamy yellow-orange to pink; a round or oval shape; margins that are distinct and sharply demarcated,
optic disc (or optic papilla)
normally include a paired artery and vein extending to each quadrant, growing progressively smaller in caliber as they reach the periphery
retinal vessels
is located on the temporal side of the fundus
macula
, the area of sharpest and keenest vision
fovea centralis
light rays are refracted through the transparent media (cornea, aqueous humor, lens, and vitreous body) and strike the retina.
visual pathway
is the normal constriction of the pupils when bright light shines on the retina. It is a subcortical reflex arc (i.e., we have no conscious control over it); the sensory afferent link is CN II (the optic nerve), and the motor efferent path is CN III (the oculomotor nerve).
pupillary light reflex
When one eye is exposed to bright light, a direct light reflex (constriction of that pupil) and a consensual light reflex (simultaneous constriction of the other pupil) occur.
one eye is exposed to bright light
is a reflex direction of the eye toward an object attracting our attention. The image is fixed in the center of the visual field, the fovea centralis.
-ocular movements are impaired by drugs, alcohol, fatigue, and inattention.
Fixation
is adaptation of the eye for near vision. It is accomplished by increasing the curvature of the lens through the muscles of the ciliary body
Accommodation
glasslike quality decreases the ability of the lens to change shape to accommodate for near vision, a condition termed?
-decrease in power of accommodation with aging, is suggested when the person moves the card farther away.
presbyopia
70 years of age the normally transparent fibers of the lens begin to thicken and yellow; this is the beginning of a (no pain)
cataract.
—a clouding of the crystalline lens partly due to ultraviolet radiation. This is curable with lens replacement surgery,
-appear as opaque black areas against the red reflex
Cataract formation ( causes of decreased visual functioning)
—an optic nerve neuropathy characterized by loss of peripheral vision, caused by increased intraocular pressure. (no pain)
Glaucoma (causes of decreased visual functioning)
—a loss of central vision caused by yellow deposits (drusen) and neovascularity in the macula. AMD prevalence rises sharply with older age; by age 80 years,
-Peripheral vision is not affected;
unable to read books or papers, sew, or do fine work and has difficulty distinguishing faces
Age-related macular degeneration (AMD)(causes of decreased visual functioning)
—the leading cause of blindness
Diabetic retinopathy
is not being able to see letters on the eye chart at line 20/50 or below
Visual impairment (VI)
(“cross-eye”)
strabismus
(“lazy eye”)
amblyopia
are common with myopia or after middle age as a result of condensed vitreous fibers.
-(“shade” or “cobwebs”) occurs with retinal detachment.
Floaters
Halos around lights occur with
acute narrow-angle glaucoma.
a blind spot inside an area of normal or decreased vision, occurs with glaucoma and optic nerve disorders.
Scotoma
occurs with optic atrophy, glaucoma, vitamin A deficiency.
Night blindness
(pain, floaters, blind spot, loss of peripheral vision)
Sudden onset of eye symptoms
is the inability to tolerate light
Photophobia
perception of two images of a single object. Diplopia in one eye is caused by dry eyes, uncorrected refractive error, cataract. Binocular diplopia, seen only when both eyes are open, occurs with misalignment of axes of eyes.
Diplopia
Redness occurs with
conjunctivitis
Lacrimation (tearing) and epiphora (excessive tearing) are caused by
irritants or obstruction in drainage of tears.
is thick and yellow.
Purulent discharge
Genital herpes and gonorrhea have
risk of eye disease for the newborn
test screens for loss of peripheral vision
-occur with diseases of the retina and with stroke.
Confrontation Test
test near vision with a handheld vision screener with various sizes of print (e.g., a Jaeger card)
- people older than 40 years
- normal result is “14/14” in each eye
Near Vision
Snellen alphabet chart is the most commonly used and accurate measure of visual acuity
-20/20 normal visual acuity
Snellen Eye Chart