HLTH 2501: the eye Flashcards
what is the eye protected by?
the body orbit of the skull
muscle of the upper eyelid
the levator palpebrae superioris
what is the levator palpebrae superior controlled by?
the oculomotor nerve (III)
cranial nerves controlling the extrinsic eye muscles
III, IV, and VI
outer layer of the eye
is a tough, fibrous layer consisting of the cornea and the sclera
middle layer of the eye
aka the uvea; is made up of the choroid, the ciliary body, and iris
the choroid
is a dark, vascular layer that absorbs the light, preventing reflection
what supplies blood to the retina?
the choroid
ciliary processes
secrete aqueous humor
two muscles in the iris
the circular (contracts) and the radial (dilates)
lens
is a biconvex structure made up an elastic capsule surrounding an orderly alignment of fibres
retina
the inner layer that consists of the pigmented layer and the neural layer
fovea centralis
is a depression within the macula lutea that contains many cones and provides the most acute vision
colour blindness
is common in males and results from a deficit of one type of cone owing to an abnormal gene on the X chromosome
posterior cavity
is the space between the lens and the retina and contains the vitreous humor
anterior cavity
is between the cornea and the lens and is filled with aqueous humor and is further divided into the anterior chamber (cornea to iris) and the posterior chamber (iris to lens); the chambers are connected through the pupil
where is aqueous humor secreted from and where is it drained into?
secreted from the ciliary processes into the posterior chamber and drained from the anterior chamber by the canal of Schlemm
what does the aqueous humor supply?
nutrients to the lens and cornea because they lack blood vessels
complications of conjunctivitis
meningitis, cellulitis, septicemia, otitis media, pneumonia, and keratitis
otitis media
ear infection
what provides depth perception?
the double image projected rom different angles by both eyes
what pass through the optic disc?
the central retinal artery and vein
diagnostic tests for eye function
the snellen chart, visual field tests, tonometry, ophthalmoscope, gonioscopy measures, and muscle function and coordination
the snellen chart
consists of line of progressively smaller letters and numbers, measuring visual acuity
what are visual field tests used for?
to check central and peripheral vision
tonometry assessment
assess intraocular pressure by checking the resistance of the cornea
ophthalmoscope
is used to examine the interior structures of the eyes
gonioscopy
measures the angle of the anterior chamber
myopia
is nearsightedness and occurs when the image is focused in front of the lens; corrected with concave lens
hyperopia
is farsightedness and occurs when the image focuses behind the retina; is corrected with convex lens
presbyopia
is farsightedness associated with aging when the loss of elasticity reduces accommodation
astignmatism
develops from an irregular curvature in the cornea or lens
strabismus
results from a deviation of one eye, resulting in double vision; this is cross-eye
diplopia
aka double vision
what may strabismus be caused by?
a weak or hypertonic muscle, a short muscle, or a neurological defect
amblyopia
is the suppression by the brain of the visual image from the affected eye
nystagmus
is an involuntary abnormal movement of one or both eyes; can be back and forth, jerky, or circular
what does nystagmus result from?
neurologic causes, inner ear or cerebellum disturbances, or from drug toxicity
ptosis
is paralysis of the upper eyelid
stye
is an infection involving a hair follicle on the eyelid, forming a swollen, red mass which may be uncomfortable when blinking
what is a stye caused by
usually a staphylococci
conjunctivitis causative organisms
most are bacteria or an adenovirus, but can also be herpes simplex virus, varceilla-zoster virus, and coronavirus
conjunctivitis
is a superficial inflammation or infection lining the eyelids and covering the sclera
what causes pink eye?
S aureus
pinkeye
is spread by fingers or towels and causes the sclera of the eye and eyelid to appear red and for purulent discharge to develop
contact lenses and infection
can cause conjunctivitis and keratitis
what infections may cause infection of the eyes in newborns?
chlamydia trachomatis and gonorrhea; this causes redness and heavy discharge from the eyes
trachoma
is a infection of the eyes that causes follicles to develop on the inner surface if the eyes and is highly contagious
what is trachoma caused by?
chlamydia trachomatis
what happens if trachoma is not fully treated?
the eyelids become scarred and the lashes turn inward to abrade the cornea
most common cause of vision loss
trachoma
symptoms of trachoma
scratchy eye, no exudate, and pearl-like follicles in upper eyelid
keratitis
is an inflammation of the cornea, usually accompanied by severe pain and photophobia (this occurs because the cornea has numerous pain receptors)
what nerve supplies the pain receptors of the cornea?
trigeminal nerve V
causes of keratitis
can be infection or injury, often caused by herpes simplex virus
complications of keratitis
there is an increased risk of ulceration eroding the cornea and scar tissue interfering with vision, and possibly causing vision loss
what may damage to the cornea result from?
abrasions from foreign bodies, a damaged contact lens, or objects directly scratching the cornea
glaucoma
results from increased intraocular pressure caused by an excessive accumulation of aqueous humor and is common with aging
narrow-angle glaucoma
occurs when the angle between the cornea and the iris in the anterior chamber is decreased by factors such as an abnormal anterior insertion of the iris
acute glaucoma
may occur when there is a sudden increase in intraocular pressure and is common with pupil dilation; this is narrow-angle
chronic glaucoma
is also wide-angle glaucoma and occurs when the trabecular network and canal of schlemm become obstructed and the outflow of aqueous humor gradually diminishes; the blood flow to the retinal cells also decreases
causes of chronic glaucoma
can be a developmental abnormality, aging, or scar tissue from trauma or infected
signs of chronic glaucoma
increased intraocular pressure, loss of peripheral vision, corneal edema which leads to blurred vision, and halos around light
what may trigger acute glaucoma
adrenergic drugs such as those used for colds or hay fever (vasoconstrictors or congestion), stress, and prolonged periods in dark rooms
signs of acute glaucoma
eye eye, nausea, headache, blurred vision, and bulging cornea
chronic glaucoma treatment
regular administration of eyedrops, constricting the pupil, drugs to reduce intraocular pressure (those that inhibit carbonic anhydrase), or laser trabeculoplasty
example of eyedrops
timolol or betaxolol
treatment for acute glaucoma
surgery to remove part of the iris or to open a passageway for drainage into the canal of schlemm or laser iridotomy
function of laser trabeculoplasty
deepens the anterior chamber and thus increases the drainage of aqueous humor
cataract
occurs when the normally clear lens becomes cloudy and thus interferes with light transmission
causes of cataracts
degeneration related to aging, excessive exposure to sunlight, blows to the eyes, or material infections related to rubella or toxoplasmosis
what material infections may cause cataracts?
rubella or toxoplasmosis
indicator of cataracts
blurred vision that progresses over the visual field and becomes darker
treatment for cataracts
damaged lens can be removed and replaced by an artificial one
detached retina
is an acute problem that occurs when the retina tears away from the underlying choroid because of marked myopia, degeneration with aging, or scar tissue
what is the result of a detached retina?
the tear allows vitreous humor to flow behind the loose retinal portion, causing a cease of function of the retina as its blood supply is derived from the choroid
signs of a detached retina
no pain, but may begin with light or dark floating sports, and that a darkened or blind area that increases in size over time
treatment for a detached retina
surgery such as scleral buckling or laser therapy closes holes and reattaches the retina
macular degeneration
is a common cause of visual loss in the elderly due to degeneration at the fovea centralis, causing a lack of nutrients to pass from the choroid
causes of macular degeneration
genetic factors and environmental exposure (ex. UV rays and drugs)
2 types of macular degeneration
dry (atrophic AMD) or wed (exudative AMD)
dry macular degeneration
is more common and occurs when deposits forms in the retinal cells, gradullary destroying them
wet macular degeneration
occurs from neovascularization occurs, with the formation of abnormal, leaky blood vessels that gradually destroy the retina
diagnosis for macular degeneration
visual field tests and angiography
signs of macular degeneration
central vision with high acuity becomes blurred, then is lost and depth perception is affected; peripheral vision remains the same
treatment for dry macular degeneration
optimal nutrition and a high dose of antioxidants and zinc
treatment for wet macular degeneration
photodynamic therapy, the drug pegaptanib, and therapy using anti vascular endothelial growth factor
photodynamic therapy
is photosensitive drug plus laser that seals off neovasculature to treat wet AMD
