chap 20 - disorders of the eye (start of final unit) Flashcards
three layers of the eye
1) outer sclera
2) uveal layer
- iris, ciliary body and choroid
3) retinal layer
conjunctiva
tissue on the inner surface of the eyelids
cornea
light enters, first refraction
lens
second site of refraction, accomodation
accomodation
by changing shape the lens can focus light rays
- Either flatten out the lens or round out the lens, important for when you are looking at something in the distance versus something close up
pupil
controlled by your iris which is made of smooth muscle
- controls how much light is allowed into the eye
retina
photoreceptors
macula
post on the retina that provides the greatest visual acuity, most cones are located here
fovea
central portion of the macula
aqueous humor
watery fluid that nourishes and cleanses the avascular lens and retina
- continually recirculating
lacrimal gland
keeps eyes moist, flush foreign debris away, produce mucus that allows eyelid to slide smoothly over eye
lens and accomodation
lens changes shape by ciliary muscle
most frequent and serious problems
- decrease in visual acuity
- Age-related macular degeneration
- Trauma
- Acute conjunctivitis
- Cataract
- Glaucoma
symptoms and signs
Decreased visual acuity resulting from:
Visual field defects
Focal areas of blindness
Pain
Manifestation of trauma, infection or increased intraocular pressure
Blurred vision
Accompanies various systemic diseases
Strabismus
amblyopia
nystagmus
strabismus
“Crossed eyes”
Etiology
- Eye muscles don’t work together - 6 different muscles on each eye
- Confuses the brain
- Brain ignores image from weaker eye
Amblyopia “lazy eye”
nystagmus
Fast, uncontrollable eye movements
One eye or both eyes
Etiology
- Congenital
- Acquired
- Head injury
- Stroke
- Inner ear disorders
- drugs/medication
tests
Visual acuity tests
Ophthalmoscope
- Used to examine the retina
Tonometer
- Measures intraocular pressure
Slit-lamp
- Used to examine the cornea, iris, and lens
refraction disorders
hyperopia, myopia, presbyopia, astigmatism
hyperopia
(farsighted)
Can see far things
Trouble seeing close things
Eyeball is too short
myopia
(nearsighted)
Trouble seeing far things
Eyeball is too long
presbyopia
Accommodation changes
Age
general symptoms of refraction disorders
General
Poor vision
Headaches
Eyestrain
Fatigue
Burning
symptoms of myopia
Blurred vision
Squinting when looking at distance objects
hyperopia symptoms
- difficulty focusing on near objects
treatment
Procedures
- Laser-assisted in situ keratomileusis (lasik)
- Both types of disorders
- Phakic intraocular lens implant
- Nearsightedness
- Myopia
- Concave lens
- Hyperopia
- Convex, lens
- Astigmatism
- Glasses or hard contact lenses
- Presbyopia
- Reading glasses or bifocal lenses
conjuctivitis
Inflammation = can be bacterial, fungal, viral or related to allergy
- Most commonly associated with bacteria and most often found in children
- Contagious
- Treated with antibiotics
Also known as: pink eye
corneal keratitis
Infection (bacteria, viral, fungus, protozoa)
Typically unilateral
Can lead to vision loss from scarring
Keratin gets into the cells of the cornea = could be from infection
corneal keratopathy
(band keratopathy)
Deposition of calcium salts within cornea
Leads to pain, decreased acuity
corneal dystrophy
Bilateral
Genetic - which is why it affects both eyes
Abnormal accumulation in cornea
Clouding of cornea
Could be treated with a cornea transplant - doesn’t have to be a specific match because the immune system doesn’t go into the anterior chamber of the eye
cataracts
= opacity of lens
- Age related degeneration - constant UV light coming into the eye over long periods of time
- Leading cause of blindness in adults worldwide
- Age associated
- By 65, 90% adults will have some
Symptoms
- Pupil looks milky white
Treatment
- Surgery = swap out the old lens for a new lens
glaucoma
Optic nerve is damaged by abnormally increased intraocular pressure (IOP)
- Irreversible
Second most common cause of blindness in world
Build up of aqueous humor
- Intraocular pressure
Signs and symptoms
- Acute glaucoma: possible loss of vision within 1 day = emergency
- Severe eye pain
- Blurred vision
- Eye redness
- Light halos
- Nausea
- Vomiting
- Risk factors
- Age
- Refractive disorders
- Genetics
Other diseases
- Hypertension
-Diabetes
retinal detachment
Retinal peels away from underlying support tissue
Medical emergency
- Can lead to blindness
Symptoms
- Spots, floaters, flashes of light
- Not painful
Surgical treatment to reattach
Etiology
- Trauma to eye
- Genetic disease - Marfan syndrome - disease of connective tissue, the CT is too weak to hold on to the retina
- Extreme nearsightedness
macular degeneration
Leading cause of vision loss in people over 60
Damage to macular - only one part but one of the most important parts
- Does not lead to complete loss of vision
Risk factors
- Age-associated
- Obesity
- UV light exposure - why its important to wear sunglasses
- Smoking
- Family history
- Ethnicity
Treatment
- No cure - try to prevent it from happening
hypertensive retinopathy
Etiology
- Damage to retina due to hypertension - high blood pressure causes pathology of the retina
- Vessel narrowing
- Microinfarcts = small areas of tissue death
- Hemorrhages
- exudates/edema = fluid leakage
Leads to:
- Dim vision
- Vision loss
- Double vision
Can be reversible with treatment - bring blood pressure down
diabetic retinopathy
Retina sensitive to hyperglycemia
- Diabetes 20x to go blind than non-diabetics
- Damage to blood vessels in cornea
Can lead to:
- Microhemorrhages = small bleeding
- Edema
- Neovascularization = new blood vessels, we don’t want a lot of blood vessels in the eye because they can interrupt light waves coming in
Symptoms
- spots/floaters in eyes
- Blurred vision
- Empty spot in vision
Treatment
- Blood glucose control
- Surgery
- Seal leaking vessels
eye diseases in diabetics
glaucoma, retinal detachment, diabetic retinopathy
color deficient (blindess)
Color vision determined by cones
- Three types (red, blue, and green cones)
- Depends on relative output of these three types of cones
X-linked recessive = more common in men, most receive from their mothers
Types
- Red-green color vision defects - most common
- Defects in…
- Either red cone output or green cone output - one or the other
- Blue-yellow color vision defects
- Trouble differentiating shades if blue and green
- Complete absence of color vision
- No working cones = only black and white
retinoblastoma
Children
Rare malignant tumor of retinal cells - usually the cones
Autosomal dominant inheritance
- Rb1 gene
Treatment = remove the eye = want to treat it early so it does not metastasize to the brain (which is super close by)
malignant melanoma
Adults
Ocular melanoma
Arise from melanocytes - just like in the skin
- Choroid layer
- Iris
Worse prognosis than skin melanoma - because it metastasizes early
organ failure - blindness
Defined as visual acuity 20/200
4/1000 people legally blind
Causes
- Lesions
- Developmental
- Trauma
