Class notes eyes Flashcards
What protects the eye?
Bony orbital cavity
Additional protection from—eyelids (injury, strong light, dust); and lacrimal apparatus
What kind of vision do humans have?
Human have a binocular, single-image visual system
Extraocular muscles (EOMs) movements:
straight and rotary movement
conjugate movement—parallel axis of movement in both eyes
Movement of EOMs stimulated by three cranial nerves:
CN VI (abducens) CN IV (trochlear) CN III (oculomotor)
3 layers of eye:
Sclera; choroid; retina
outer layer of eye:
sclera
Sclera characteristics:
tough protective white covering
Continues anteriorly as smooth
transparent cornea
Cornea does:
refracting medium—bends light rays to focus on retina
Corneal reflex:
stimulation of cornea causes blinking
Nerves for blinking:
CN V (trigeminal)—afferent sensation to brain CN VII (facial)—efferent message-stimulates blinking
Middle layer of eye:
Choroid
Choroid characteristics:
Darkly pigmented
Continuous anteriorly with iris
Highly vascularized—delivers blood to retina
Iris:
Controls amount of light admitted to retina
Iris bright/dark light:
In bright light—the eye contracts and accommodates for near vision
In dim light—the eye dilates and accommodates for far vision
Pupil size reacts to:
Amount of ambient light and accommodation
Pupil is:
round, regular
Parasympathetic and sympathetic nervous system determines what in pupil:
Size
Stimulation of parasympathetic—through CN III causes pupil to:
pupil constricts
Stimulation of sympathetic pupil:
pupil dilates, eyelid elevates
Lens of eye is:
biconvex disc posterior to pupil
Serves as refractory medium—bulges for focusing on near objects
flattens for far objects
Inner layer of eye:
Retina
Retina function:
light waves changed into nerve impulses
Retinal structures viewed with ophthalmoscope:
Viewed: optic disc; retinal vessels; general background; macula
What determined by balance between amount of aqueous humor produced and resistance to outflow at angle of the anterior chamber?
Intraocular pressure
What does the aqueous humor do?
Nourishing the cornea and the lens by supplying nutrition such as amino acids and glucose
Maintain intraocular pressure.
Transport Vitamin C in the front segment to act as an anti-oxidant agent.
Pupillary Light Reflex tests which nerves?
CN II (optic)—sensory afferent link CN III (oculomotor)—motor efferent path
With different light reflex, what occurs?
consensual light reflex occurs
What is accommodation?
adaptation of the eye for near vision; convergence of axes of the eyes when changing focus from far vision to near vision
Examine for accommodation?
focus on distant object (pupils dilate) and then shift gaze to near object (Such as finger) caused pupillary constriction and convergence
When does macula Macula mature?
absent at birth; mature by 8 mo.
Eye movements in infant:
poorly coordinated
binocularity established at what age in infants?
3-4 months
% of infants born with farsightedness:
80%
When does farsightedness decrease in children?
this decreases by age 7-8
What happens to lens in aging adults?
Lens loses elasticity—becomes hard and glass-like
Increase or decreased ability to change shape to accommodate for near vision in aging adult?
decreased
What age does 50% of aging adults develop presbyopia (farsightedness)?
By age 40
So may need images magnified
What age does normally transparent fibers of lens begin to thicken and yellow?
By age 70
Cataracts
What is arcus senilis?
Narrow opaque band encircling cornea
Common in old age
Most common causes of decreased visual functioning?
Cataract formation
Glaucoma
Age-related macular degeneration (AMD)
Diabetic retinopathy
Age-related macular degeneration (AMD) is?
Yellow deposits & neovascularity in macula; loss of central vision
Optic nerve neuropathy; loss of peripheral vision caused by ↑IOP is called?
Glaucoma
What do you ask about eyes for sub data:
Vision changes; pain Ask about acute onset of floaters, halos around lights, loss of peripheral vision, blind spot
What is Strabismus?
misalignment of eyes, inward or outward
What is diplopia?
double vision
Ask about these things in eye sub data:
Redness, swelling—one or both eyes, watering, discharge
Ask about vaginal infections in mother at time of delivery such as:
genital herpes, GC lead to risk for eye disease in the newborn
test for visual acuity:
Snellen eye chart
20 feet away
Vision parameters:
Normal visual acuity—20/20
Poor than 20/30—refer to eye provider
impaired vision: 20/50
Vision impairment due to:
Refractive error
Opacity in the media (cornea, lens, vitreous)
Disorders in the retina or optic pathway
Visual field test is testing for:
Testing for peripheral vision loss
In older adult—screen for glaucoma
Diagnostic Positions Test:
Lead the eyes through six cardinal position of gaze to determine any EOM weakness
There should be parallel tracking with both eyes
nystagmus
fine oscillating movement (can be seen with ear or eye disease; MS; brain lesions; overdose of phenytoin)
3 things to assess in eye:
Check lateral canthus (corner of eyes) for pallor
Check sclera for jaundice
Check if pupils are equal
What is anisocoria? How many have it normally?
Unequal pupil size, 5% have anisocoria normally
