Chapter 15: Eyes Flashcards
The extraocular muscles function:
- Six muscles attach eyeball to its orbit and direct eye to points of a person’s interest
- gives eye straight and rotary movement
The three concentric coats of the eyeball are:
- Sclera
- Choroid
- Retina
The functions of the eye are:
- Ciliary body: the muscles of the ciliary body control the thickness of the lens.
- Pupil: controls the amount of light admitted into the retina.
- Iris: functions as a diaphragm, varying the opening of the pupil.
The image formed on the retina is:
-Upside down and reversed from its actual appearance in the outside world.
The lacrimal apparatus provides:
-Constant irrigation to keep the conjunctiva and cornea moist and lubricated.
-The lacrimal gland:
-secretes tears, which wash across the eye, and then eventually drain into the puncta at the inner canthus
The lacrimal system consists of:
- Pupillary light reflex: the normal constriction of the pupils when bright light shines on the retina. (Can be direct or consensual)
- Fixation: a reflex direction of the eye toward an object attracting a person’s attention. (The image is fixed in the center of the visual field, the fovea centrali).
- Accommodation: the adaptation of the eye for near vision. Movement of the ciliary muscles increases the curvature of the lens. Observed through convergence (motion toward) of the axes of the eyeballs and constriction of the pupils.
What occurs when one eye is exposed to bright light and its pupil constricts?
-Direct light reflex of the pupil
What occurs when one eye is exposed to light and the other eye’s pupil constricts simultaneously?
-Consensual light reflex of the pupil
Decreased visual changes in the older adult occur in:
- Cataract formation
- Glaucoma
- Macular degeneration.
Normal visual acuity of 20/20:
- the top number indicates:
- the bottom number indicates:
- top: the distance the person is standing from the chart
- bottom: gives the distance at which a normal eye could have read a particular line on a chart.
“20/20” means:
-That one can read at 20 feet what the normal eye could have read at 20 feet.
How do you test for presbyopia:
- Use a handheld vision screener with various sizes of print.
- Hold the card, while in good light, about 14 inches from the eye—this distance equals the print size on the 20-foot chart.
- Test each eye separately, with glasses on.
- If no vision screening card is available, ask the person to read from a magazine or newspaper
What is a mild weakness noted when fusion is blocked called?
-Phoria
What is a weakness noted when fusion is blocked that is worse than in phoria called? A constant malalignment of the eyes?
-Tropia
Abnormal findings of the sclera can include: (1)
-Scleral icterus is an even yellowing of the sclera that extends up to the
cornea, indicating jaundice.
What is pingueculae?
- nodules on the sclera
- they are yellowish elevated nodules that are due to a thickening of the bulbar conjunctiva from exposure to sun, wind, and dust.
- They appear at the 3 and 9 o’clock positions, first on the nasal side, then on the temporal side
What is Pterygium?
- A triangular, opaque wing of bulbar conjunctiva that grows toward the center of the cornea.
- It usually develops from the nasal side, and may obstruct vision if it covers the pupil.
- It is caused by chronic exposure to a hot, dry, sandy climate, which stimulates the growth of a pinguecula into a pterygium
The unit of strength of each lens is called the:
-Diopter
The black numbers:
-Indicate a positive diopter and focus on objects nearer in space to the ophthalmoscope.
The red numbers:
-Show a negative diopter and are used for focusing on objects farther away.
Testing for strabismus (squint or crossed eye) is an important screening measure during:
- Early childhood years because diagnosis after age 6 has a poor prognosis for correction.
- Early recognition and treatment are essential for restoration of binocular vision.
What is an excess skinfold extending over the inner corner of the eye, partly or totally overlapping the inner canthus? (It occurs frequently in Asian children and in 20% of whites, and eventually disappears in non-Asian children with growth.)
Epicanthal fold
Definition: The presence of epicanthal folds gives a false appearance of malalignment, but the corneal light reflex is normal
Pseudostrabismus
(conjunctivitis of the newborn) What is a purulent discharge due to a chemical irritant or bacterial or viral agent from the birth canal?
Ophthalmia neonatorum:
What are white specks noted around the edge of the iris, that may occasionally be normal but usually suggest Down syndrome?
Brushfield’s spots
What is cranial nerve VI and what does it do?
-Abducens nerve, innervates lateral rectus muscle, which abducts eye
What is cranial nerve IV and what does it do?
-Trochlear nerve, innervates superior oblique muscle
What is cranial nerve III and what does it do?
-Oculomotor nerve, innervates all the rest: the superior, inferior, and medial rectus and the inferior oblique muscles
What is the cornea and what does it do?
-Part of refracting media of eye, bending incoming light rays so that they will be focused on inner retina
What is cranial nerve VII and what does it do?
- Facial nerve
- Carries efferent message that stimulates blink
What is cranial nerve V and what does it do?
- Trigeminal nerve
- Carries afferent sensation into brain.
What reflex is this? Contact with a wisp of cotton stimulates a blink in both eyes.
Corneal reflex
What is the outer fibrous that is a tough, protective, white covering that is continuous
anteriorly with the smooth, transparent cornea and covers iris and pupil?
-Sclera
What is the middle vascular layer of they eye that delivers blood to the retina. Also, anteriorly, this structure is continuous with the ciliary body and the iris?
Choroid
What is the inner nervous layer of the eye which is the visual receptive layer of the eye in which light waves are changed into nerve impulses?
Retina
What does the muscles of the ciliary body do?
-Control the thickness of the lens
What is the purpose of the pupil?
-To control the amount of light admitted into the retina.
What is the purpose of the iris?
-To function as a diaphragm, varying the opening of the pupil.
What part of the eye provides constant irrigation to keep the conjunctiva and cornea moist and lubricated?
-Lacrimal apparatus
What gland secretes tears, which wash across the eye, and then eventually drain into the puncta at the inner canthus?
-Lacrimal gland
What is the normal constriction of the pupils when bright light sines on the retina called (can be direct or consensual)?
-Pupillary light reflex
What is the reflex direction of the eye toward an object attracting a person’s attention called?
-Fixation
What is the adaption of the eye for near-vision which works by the ciliary muscles increasing the curvature of the lens called? is the reflex direction of the eye toward an object attracting a person’s attention called?
-Accommodation
What is another word for “motion toward?”
-Convergence
What is the condition of impairment of vision as a result of old age called?
-Presbyopia
What is the delicate membrane lining the eyelids and covering the eyeball called?
-Conjunctiva
What can general reddening of the conjunctiva indicate?
- conjunctivitis
- bacterial or viral infection
- allergic reaction
- chemical irrigation
What can cyanosis of the lower lids indicate?
-Hypoxemia
Pallor near the outer canthus of the lower lid may indicate ________?
-Anemia
Which one typically has more pigment: inner or outer canthus?
-Outer canthus
What is yellowing of the sclera due to jaundice called?
-Scleral icterus
