Chapter 15 - Eyes Flashcards
Which eyelid (upper/lower) is more mobile?
upper
What do eyelashes filter?
dust and dirt
What is the palpebral fissure?
open space between the eyelids
What is the limbus?
the border between the cornea and sclera
What is the canthus?
corner of the eye, angle where eyelids meet
What is the caruncle?
small fleshy mass containing sebaceous glands
What are the tarsal plates?
strips of connective tissue that give the upper eyelid shape
Where are the meibomian glands?
in the tarsal plates
What are meibomian glands?
modified sebaceous glands that lubricate eyelids
What do the meibomian glands do?
stop tears from overflowing, create airtight seal when eyes are closed
What is the conjunctiva?
transparent protective covering of the eye, thin mucous membrane
Where is the palpebral conjunctiva?
lines the eyelids, is clear
The palpebral conjunctiva had many ________ _______
blood vessels
Where is the bulbar conjuctiva?
overlies eyeball, sclera shows through
What is the role of the cornea?
protect iris and pupil
What does the lacrimal apparatus do?
provide constant irrigation to maintain moisture and lubrication
Where do tears drain?
the puncta
Where do the tears go after the puncta?
nasolacrimal sac, nasolacrimal duct, empty into inferior meatus in nose
What prevents air being forced into the nasolacrimal duct when the nose is blown?
tiny fold of mucous membrane
How many muscles attach the eye to its orbit?
6
What do extra ocular muscles allow?
straight and rotary movements
Name the 4 straight (rectus) muscles of the eye?
- superior
- inferior
- lateral
- medial
Name 2 slanting (oblique) muscles of the eye?
- superior
- inferior
What is conjugate movement of the eye?
each muscle is coordinated with the one in the other eye and ensures the axes remain parallel
Why are parallel axes important?
the human brain can tolerate seeing only one image
What kind of vision do humans have?
binocular, single-image
How many cranial nerves stimulate movement of the extra ocular muscles?
3
Which cranial nerve innervates the lateral rectus muscle?
CN VI abducens nerve
What does the lateral rectus muscle do?
abducts the eye (laterally towards temple)
Which cranial nerve innervates the superior oblique muscle?
CN IV (trochlear nerve)
What does the superior oblique muscle do?
moves the eye downward and inward toward the nose
Which cranial nerve innervates the superior, inferior, and medial rectus and all inferior oblique muscles?
CN III (oculomotor nerve)
What does the superior oblique muscle do?
look downward and inward
What are the 3 layers of the eye from superficial to deep?
sclera, choroid, retina
Which eye layer is vascular?
choroid
How can you examine the retina?
opthalmoscope
What is the sclera?
a tough, protective, white covering
What does the cornea do?
protect and refract light
What is the corneal reflex?
touch to the cornea stimulates a blink in both eyes
Which cranial nerves are involved in the corneal reflex?
CN V (trigeminal) carries sensation to the brain and CN VII (facial nerve) stimulates the blink
Why is the choroid darkly pigmented?
to prevent light from reflecting internally
What do the muscles of the ciliary body control?
thickness of the lens
What does the iris do?
controls the opening where light gets in
The iris ______ in bright light and to acomodate for near vision
contracts
Darker irises = darker _________
retina
Which part of the nervous system controls pupil size?
autonomic nervous system
Parasympathetic stimulation via CN ____ = pupil __________
III; constriction
Sympathetic stimulation = pupil __________
dilation
The lens _____ for focusing on near objects and ________ for far objects
bulges; flattens
Where is the anterior chamber?
posterior to the cornea, but anterior to iris and lens
Where is the posterior chamber?
behind iris, to the sides of the lens
Where is the aqueous humour in the chambers produced?
ciliary body
What does aqueous humour do?
deliver fluid and nutrients to surrounding tissues
What determines intraocular pressure?
balance between amount of aqueous humour and outflow at the angle of the chamber
Where are light waves changed into nerve impulses?
retina
What is the optic disc?
area where fibres from retina converge to form the optic nerve
Where is the optic disc located?
towards nasal side of retina
Optic Disc characteristics:
-yellow-orange to pink colour
-round or oval shape
-distinct margins
-physiological cup
Where is the macula located?
on the temporal side of the fundus
What is the macula?
darker pigmented region surrounding the fovea
What is the fovea centralis?
area of sharpest and keenest vision
What does the macula do?
receive and transduce light into neural signals
The image formed on the retina is ______ _____ and _______
upside down, and reversed
What happens at the optic chiasm?
nasal fibres cross over, left optic tract has fibres from left half of each retina, and right optic tract contains fibres from the right half
The right side of the brain looks at the _____ side of the world
left
What is the pupillary light reflex?
normal constriction of the pupils when bright light shines on the retina
The pupillary light reflex is a subcortical reflex arc meaning…
a person has no conscious control over it
Bright light = direct light reflex…
constriction of THAT pupil
Consensual light reflex
simultaneous constriction of the OTHER pupil
What is fixation?
a reflex direction of the eye toward an object attracting a person’s attention
What is accomodation?
adaptation of the eye for near vision
How does accommodation work?
increasing curvature of the lens via ciliary muscles
When does the macula begin developing?
age 4 months
When does the macula mature?
age 8 months
When does the infant establish binocularity and can fixate on a single image?
3 to 4 months
Most neonates are born __________ but this gradually decreases
farsighted
When does the eyeball reach adult size?
8 years of age
Presbyopia
lens becomes hard and this decreases its ability to change shape and accommodate near vision
The average onset of presbyopia is _____
40yo
By age 70 the lens thickens and yellows, this is called…
nuclear sclerosis (beginning of a senile cataract)
Macular degeneration
breakdown of cells in the macula that causes loss of central vision
What is the most common cause of blindness?
age-related macular degeneration
What increases risk for menopause?
-women, especially early menopause
With AMD is peripheral vision affected?
no, only sharp, straight vision
What is cataract formation?
lens opacity
What causes cataracts?
clumping of proteins in the lens
What age is cataract formation expected?
70 years old
What are risk factors for cataracts?
-age
-diabetes mellitus
-steroids
-ocular trauma
-previous surgery
What is glaucoma?
increased intra ocular pressure
What is chronic open-angle glaucoma?
most common form of the disease, involving damage to the optic nerve
__________ retinopathy is the leading cause of visual impairment in people under 65
diabetic
Visual acuity worse than 20/___ disqualifies people from obtaining a drivers license in Canada
50
What is it called when vision can’t be corrected better than 20/200 or better than 20 degrees?
legal blindness
Risk factors for glaucoma:
->60 yoa
-being of African descent
-being a woman
-increased intra ocular pressure (>21mmHg)
-family history
-steroid use
-hypertension
-eye injury
-severe myopia
-diabetes
Aqueous humour originates in which chamber and moves to…
starts in posterior chamber moves to anterior chamber
How does IOP increase?
if fluid flow is blocked
Which type of glaucoma is most common?
open-angle glaucoma
What is open-angle glaucoma?
angle between iris and cornea is open but fluid is slow to drain
What is closed angle glaucoma?
when space between cornea and iris is narrower than normal
Are there any symptoms that warn of open-angle glaucoma?
no
What are the symptoms of closed angle glaucoma?
blurred vision, sensitivity to light, nausea, halos around the eyes
None of the Canadian provinces cover the cost of eye exams for people age ___-___
20-64
Floaters occur with…
myopia or after middle age as a result of condensed vitreous fibres
Halos around lights occur with…
acute narrow-angle glaucoma
What is scotoma?
a blind spot in the visual field surrounded by an area of normal or decreased vision
Scotoma occurs with…
glaucoma and disorders of the optic nerve
Night blindness occurs with…
optic atrophy, glaucoma, or Vit A deficiency
Photophobia
inability to tolerate light
Strabismus
a deviation in the anteroposterior axis of the eye
Diplopia
double vision
Epiphora
excessive tearing
Which 2 diseases are a risk to newborn vision?
herpes and gonorrhoea
If a patient misses 1 or 2 letters on the smallest line they can read does it count?
yes, their vision is still equal to that line
What does 20/20 vision mean?
you can read at 20 feet what the normal eye can at 20 feet
What does the confrontation test measure?
peripheral vision
What are normal results of the confrontation test?
-50 degrees upward
-90 degrees temporal
-70 degrees downward
-60 degrees nasal
What does the corneal light reflex test?
parallel alignment of the eye axes
What does the cover-uncover test detect?
small degrees of deviated alignment
What does the diagnostic positions test reveal?
muscle weakness during movement
Nystagmus
fine oscillating movement seen around the iris
When is mild nystagmus normal?
extreme lateral gaze
Lid Lag
white rim of sclera seen between the eyelid and iris during eye movement
When is eversion of the upper eyelid used?
when inspecting conjunctiva in case of pain or suspicion of foreign body
Aniscoria
having pupils of two different sizes
What should you note about pupil size in the acute care setting?
record size in mm to compare changes
PERRLA
pupils equal round react to light and accomodation
What is the unit of strength of each lens is the ______
dioptre
Red Reflex
red glow filling the pupil caused by the reflection of your ophthalmoscope light
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