eyes Flashcards
external anatomy of the eye
the bony orbital cavity surrounded by cushion of fat that protects the eye
external anatomy of the eye - palpebral fissure
Palpebral fissure:
◦ Elliptical open space between eyelids
external anatomy of the eye - corneal limbus
Lower lid margin, at limbus, borders between
cornea and sclera
external anatomy of the eye - canthus
◦ Canthus: corner of eye, angle where lids meet
◦ Inner canthus: caruncle is small fleshy mass
containing sebaceous glands
anatomy of the external eye - tarsal plate
◦ contain meibomian glands, which are modified sebaceous glands that secrete an oily lubricating material onto lids
anatomy of the external eye - conjunctiva
- transparent protective covering of the eye
anatomy of the external eye - cornea
covers and protects the iris and pupil
anatomy of the external eye - lacrimal apparatus
provides irrigation to the eye
extraocular muscles
- Give eye both straight and rotary movement
- Each muscle is coordinated, or yoked, with one in other eye ensuring that when two eyes
move, their axes always remain parallel, called
conjugate movement - Four straight, or rectus, muscles are superior,
inferior, lateral, and medial rectus muscles - Two slanting, or oblique, muscles are
superior and inferior muscles
how many extraocular muscles are there (exam)
Six muscles attach eyeball to its orbit and direct eye to points of a person’s
interest
why are parallel axis important for the extraocular muscles (exam)
Parallel axes are important because
human brain has a binocular, single image visual system
what is movement of the extraocular muscles stimulated by (exam)
◦ Cranial nerve VI: abducens nerve, innervates lateral rectus muscle, which abducts eye
◦ Cranial nerve IV: trochlear nerve, innervates superior oblique muscle
◦ Cranial nerve III: oculomotor nerve, innervates all the rest: the superior, inferior, and medial rectus and the inferior oblique muscles
internal anatomy of the eye
Eye: a sphere of three concentric coats
Outer fibrous sclera
Middle vascular choroid
Inner nervous retina
Inside the retina is a transparent vitreous body.
The only parts accessible for examination are the sclera anteriorly and the retina through the ophthalmoscope.
sclera
Sclera: tough, protective, white covering
◦ Continuous anteriorly with smooth, transparent cornea, which covers iris and pupil
cornea
Cornea: part of the refracting media of eye, bending incoming light rays so that they will be focused on
inner retina
◦ Corneal reflex—contact with a wisp of cotton stimulates a blink in both eyes
◦ Trigeminal nerve, cranial nerve V, carries afferent sensation into brain.
◦ Facial nerve, cranial nerve VII, carries efferent message that stimulates blink.
the middle layer - choroid
has dark pigmentation to prevent light
from reflecting internally and is heavily
vascularized to deliver blood to retina
the middle layer - iris
Iris: functions as a diaphragm, varying opening
at its center, the pupil
◦ Muscle fibers of iris contract pupil in bright light and to accommodate for near vision
◦ Dilate pupil when light is dim and for far vision
the middle layer - pupil
Pupil: round and regular; size determined by
the balance between parasympathetic and
sympathetic chains of the autonomic nervous
system
Stimulation of the parasympathetic branch, through cranial nerve III causes constriction of the pupil
Stimulation of the sympathetic branch dilates the pupil and elevates the eyelid
Pupil size also reacts to the amount of ambient light and accommodation or focusing an object on the retina
internal anatomy - lens
Lens: biconvex disc located just posterior
to the pupil
middle layer - transparent
Transparent; it serves as a refracting
medium, keeping a viewed object in
focus on the retina
Anterior and posterior chambers contain
clear, watery aqueous humor produced
continually by the ciliary body
- Continuous flow of fluid serves to deliver nutrients to surrounding tissues and to drain
metabolic wastes
Intraocular pressure determined by
balance between the amount of aqueous
produced and resistance to outflow
inner layer - retina
Retina: the visual receptive layer of eye where light waves change into nerve impulses
◦ Retinal structures viewed through
ophthalmoscope are optic disc, retinal vessels,
general background, and macula
inner layer - optic disc
Optic disc: area in which fibers from retina converge to form optic nerve
- Located toward nasal side of retina, it has
characteristics specific to color, shape and
margins
inner layer - retinal vessels
Retinal vessels: normally include a paired artery and vein extending to each quadrant
inner layer - macula
Macula: located on temporal side of fundus
◦ Slightly darker pigmented region surrounding fovea centralis, area of sharpest and keenest vision
◦ Receives and transduces light from center of visual field
visual pathways and visual fields
Light rays are refracted through transparent media, the cornea, aqueous humor, lens, and vitreous body, striking the retina
◦ Retina transforms light stimulus into nerve impulses conducted to visual cortex
◦ Image formed on retina is upside down and reversed
◦ All retinal fibers collect to form optic nerve but maintain same spatial arrangement
◦ At optic chiasm, fibers from both visual fields cross over
◦ Left optic tract now has fibers from left half of each retina, and right optic tract contains fibers only from right; thus, right side of brain looks at left side of the world
pupillary light reflex (exam)
Pupillary light reflex: normal constriction of pupils when bright light shines on retina
◦ Subcortical reflex arc with no conscious control
fixation of the eyes (exam)
Fixation: a reflex direction of eye toward an object attracting a person’s attention
◦ Image fixed in center of visual field, the fovea centralis
what is accommodation (exam)
the ability for adaptation of the eye for near vision
accommodation of the eye (exam)
◦ Accomplished by increasing curvature of lens through movement of ciliary muscles
◦ Although lens cannot be observed directly, the following components of accommodation can be observed:
◦ Convergence (motion toward) of the axes of the eyeballs
◦ Pupillary constriction
developmental competence: aging in adults
- Changes in eye structure loss of
elasticity, fat & muscle tissue atrophy
&decreased tear production - Visual acuity may diminish gradually
after age 50 and more so after age 70
Floaters appear from accumulation of
debris
what is presbyopia
Presbyopia
◦ Lens loses elasticity, becoming rigid and
glasslike, which decreases the ability to
change shape to accommodate for near
vision by age 40 to 45
what are the four most common causes of decreased visual functioning in older adults
cataract formation
diabetic retinopathy (DR)
glaucoma
Age-related macular degeneration (AMD)
cataract formation
lens opacity, resulting from a clumping of proteins in the lens
diabetic retinopathy (DR)
oxidative damage and inflammation of the retina leading to blindness
glaucoma
increased intraocular pressure leading to optic nerve compression
age-related macular degeneration (AMD)
degeneration of the cells in the macula of the retina leading to a loss of central vision
how genetics affects developmental competence of the eyes in aging adults
Culturally based variability present in color of iris and retinal pigmentation
- By age 80, most individuals in the US have cataracts or have had cataract surgery
◦ Family history & environment are risk factors
Glaucoma incidence increases with age.
◦ Black Americans 40 years & older are at highest risk, followed by Hispanic/Latinos & Whites (NIH, 2021)
what is age-related macular degeneration seen in
- Increase seen in White Americans over the
age of 75 (NIH,2021) - Diet & smoking are modifiable risk factors
how is visual impairment seen
- Not being able to see letters on the eye
chart at line 20/40 or below (NIH, 2021) - Due to uncorrected refractive error
- Most common eye problems in children
uncorrected refractive errors
(nearsightedness, farsightedness &
astigmatism)- Visual screening is crucial to detect
strabismus (“cross-eye”) & amblyopia
(“lazy eye”)
- Visual screening is crucial to detect
subjective complaints regarding vision
- Vision difficulty: decreased acuity, blurring, blind spots
- Pain
- Strabismus, diplopia
- Redness, swelling
- Watering, discharge
- History of ocular problems
- Glaucoma
- Use of glasses or contact lenses
- Patient-centered care
some vision difficulty questions to ask
Any difficulty seeing or any blurring? Blind spots?
Come on suddenly or slowly? One eye or both?
Constant, or does it come and go?
Do objects appear out of focus or clouding of
objects?
Do spots move in front of your eyes? One or
many? In one or both eyes?
Any halos, rainbows, rings around objects?
Any blind spot? Does it move as you shift your
gaze? Any loss of peripheral vision?
Any night blindness?
some questions to ask about the eye pain
Any eye pain? Please describe.
Come on suddenly?
Quality: burning or itching? Or sharp, stabbing
pain; pain with bright light?
A foreign body sensation? Or deep aching? Or
a headache in the brow area?
pain questions for strabismus, diplopia
Any history of crossed eyes?
Now or in the past?
Does this occur with eye fatigue?
Ever see double?
Constant, or does it come and go?
In one eye or both?
pain questions for redness, swelling
Any redness or swelling in the eyes?
Any infections?
Now or in the past?
When do these occur?
In a particular time of year?
questions to ask about watering or discharge of the eyes
◦ Any watering or excessive tearing?
◦ Any discharge? Any matter in the eyes? Is it hard to open your eyes in the morning? What color is the discharge?
◦ How do you remove matter from eyes?