Eyes Flashcards
Bony orbital cavity: function
Protects the eye
Eye additional protection
eyelids (injury ,strong light, dust)
lacrimal apparatus
Extraocular muscles (EOMs)
straight and rotary movement
conjugate movement—parallel axis of movement in both eyes
Movement of EOMs stimulated by three cranial nerves:
a) CN VI (abducens)
b) CN IV (trochlear)
c) CN III (oculomotor)
Eye has 3 layers:
Sclera; choroid; retina
Outer layer- Sclera
tough protective white covering
Continues anteriorly as smooth, transparent cornea
Cornea function
refracting medium—bends light rays to focus on retina
Corneal reflex and CN
stimulation of cornea causes blinking
CN V (trigeminal)—afferent sensation to brain CN VII (facial)—efferent message-stimulates blinking
Middle-Layer: choroid
darkly pigmented
Continuous anteriorly with iris
Highly vascularized—delivers blood to retina
Middle layer: Choroid: Iris function
controls amount of light admitted to retina
Middle layer: Choroid: Iris bright light
Eye contracts and accommodates for near vision
Middle Layer: Choroid: Iris in dim light
the eye dilates and accommodates for far vision
Pupil size react to
Ambient light and accommodation
Pupil Shape
round, regular
Pupil size determined by
balance b/ parasympathetic and sympathetic NS
Stimulation of parasympathetic on pupils
CN III causes pupils to constrict
Stimulation of sympathetic on pupils
CN III pupil diltes, eyelid elevates
Lens anatomy
Biconvex disc posterior to pupil
Lens function
serves as refractory medium
bulges for focusing on near objects; flattens for far objects
Inner Layer: Retina function
light waves changed into nerve impulses
How is retina viewed?
opthalmascope
What structures are viewed within retina
Optic disc, retinal vessel, general background, macula
Intraocular pressure (IOP) determined by
balance between amount of aqueous humor produced and resistance to outflow at angle of the anterior chamber
What is the function of aqueous humor
delivers nutrients to surrounding tissues
Drains metabolic waste
Helps establish intraocular pressure
Aids in light refraction as it is part of transparent media
Pupillary light reflex CN
CN II (optic)—sensory afferent link
CN III (oculomotor)—motor efferent path
Why is consensual light reflex
When one eye is exposed to bright light the other eye constricts
Can occur with unilateral blindness, blind eye doesn’t change but normal one does
Accommodation
adaptation of the eye for near vision
convergence of axes of the eyes when changing focus from far vision to near vision
pupillary constriction
How to test accommodation
Ask pt. to focus on distant object– this process dilates the pupils
Then have pt. shift gaze to close object near nose 7-8 cm
DC Infants & children eye movements at birth
Eye movements poorly coordinated at birth; by 3-4 mo—binocularity established
80% babies born
farsighted; this decreases by age 7-8
Macula (keenest vision)
absent at birth; mature by 8 mo.
DC Aging adult Lens
loses elasticity—becomes hard and glass-like
Aging adult: Near vision
Decreased ability to change shape to accommodate for near vision
By age 40, 50% have
presbyopia—so may need images magnified
By age 70, normally transparent fibers of lens begin to
thicken and yellow
Cataracts
What is arcus senilis
Commonly seen around the cornea
gray-white arc or circle around the limbus
Caused by deposition of lipids
4 common causes of decreased visual functioning
- Cataract formation
- Glaucoma
- Age related macular degeneration
- Diabetic retinopathy
Glaucoma
Causes optic nerve neuropathy damage
Loss of peripheral vision caused by increased intracocular pressure
SD: Vision changes, pain
Ask about acute onset of floaters, halos around lights, loss of peripheral vision, blind spot
SD: Strabismus, diplopia
Ask about past and current hx of
SD: redness, swelling causes
Cunjuntivis
Allergic conjuncitivitis
Iritis (circumconreal redness)
Primary angle-closure glaucoma
SD: watering, discharge
Question any purulent pus at night, excessive tearing
SD: Infants/children
Ask about vaginal infections in mother at time of delivery including:
Genital herpes
Gornorrhea
Chlamydia
OD: visual acuity test
Snellen eye chart
Position pt. client 20 feet away
OD: Visual acuity results
20/20 normal
Poorer than 20/30 refer to eye provider
Impaired vision is due to
Refractive error
Opacities in the media (cornea, lens, vitreous)
Disorders in the retina or optic pathway
What is the media
Contains the structures aid in refraction of light
OD: Visual fields test
Testing for peripheral vision loss
In older adults this also screen for glaucoma
OD: Diagnostic positions test process and results
Lead the eyes through six cardinal position of gaze to determine any EOM weakness
There should be parallel tracking with both eyes
Also note nystagmus—fine oscillating movement (can be seen with ear or eye disease; MS; brain lesions; overdose of phenytoin)
Nystagmus can be seen in
Ear or eye disease
MS
Brain lesions
overdose of phenytoin
What to check for in lateral canthus?
Pallor
What to check for in sclera?
Jaundice
Anisoocaria
5% of population has unequal pupils