Vision and Hearing Disorders Flashcards
Describe the characteristics of conjunctivitis?
- Known as pink eye
- transmitted through contaminated fingers
- redness and irritation of eye
Compare and contrast viral and bacterial conjunctivitis.
- Viral: less exudate, lasts day or weeks
- Bacterial: less common, caused by staph or strep or the flu; inflamed and produces yellow drainage
What other things can cause conjunctivitis?
chemicals or allergic reactions
How is conjunctivitis transmitted from person to person?
contaminated finger, swimming pools, and personal items
How long does viral and bacterial conjunctivitis last?
Viral: several days to two weeks
Bacterial: 10-14 days without antibiotics; 1-3 days with antibiotics
What is ophthalmia neonatorum (ON)?
- baby’s eyes become contaminated with Neisseria or chlamydia while exiting vagina.
- Erythromycin ointment put on eyes to prevent this
Layers of retina
- Neural
2. Pigmented: absorb scattered light which helps with clear images and prevents buildup of light
Name the 3 layers of neurons that make up the neural layer of the retina
-ganglion cell, bipolar neurons and the photoreceptors
How light passes through the eye
light-> retina-> blood vessels-> ganglia cells-> bipolar cells-> photoreceptors-> pigmented cells
What is a fundoscopic examination?
optic disc is located closer to the nose compared to the macula so you can tell which is the right and left eye
What are the two sources for the blood supply that feed the retina?
choreocapillaries and the central retinal artery
-fovea only receives blood from choreocapillaries
Do most diseases of the retina cause pain? Why is this significant?
Most retinopathy conditions don’t cause pain. Most people don’t go to the hospital until vision problems are so bad.
What are pericytes and what is their function on the retinal vasculature?
contractile cells just outside the endothelium that give the capillaries extra structure
Describe microaneurysms, neovascularization, and opacities
- microaneurysms: caused by weakness in the walls of the vessels because of pericyte loss
- neovascularization: occurs when the retina cells are not getting enough oxygen
- opacities: dark or cloudy areas on the retina that can be caused by bleeding, tissue proliferation, exudates, edema and something called “cotton wool spots”
Describe non-proliferative (background) and the proliferative type of diabetic retinopathy
- Nonproliferative: blood sugars are high which leads to a dysregulation of ocular blood flow
- Proliferative: follows the non-proliferative stage and is characterized by an expansion of newly formed blood vessels that are fragile and leak easily
Explain the three types of retinal detachment and describe what type is common in diabetic retinopathy
- Exudative: accumulation of fluid occurs under the neurosensory retina
- Traction: mechanical forces on the retina
- Rhegmatogenous: tear in the retina (rhegma means tear)-> vitrous seeps underneath
Explain how high blood sugar contributes to diabetic retinopathy that progresses from nonproliferative to proliferative
Glucose will get into the basement membranes making them super thick. This thickness will disrupt the intimate association of pericytes. Pericytes will die.
Treatments for retinopathy
laser photocoagulation, intravitreal injections of anti VEGF agents and vitrectomy to remove vitreous hemorrhage and vitreoretinal membranes
How often should diabetics have eye examinations? What is the best approach to prevent the progression of diabetic retinopathy and to preserve vision?
- Annually
- control blood glucose levels, hypertension, and hyperlipidemia
Recall what area of vision (central or peripheral) is affected by AMD
central
Risk factors for AMD
advancing age, family history of the disease, history of smoking, being a woman, being Caucasian, obesity, and hypertension
What form forms first in macular degeneration
dry forms first with no symptoms early on.
Explain what Drusen is, how it is formed and where it is found.
yellowish in color and builds up between Bruch’s membrane (the innermost layer of the choroid) and the pigmented epithelium.
Explain what wet AMD is and why it is more serious
new vessels are leaky, and these leaky vessels greatly contribute to the macular edema in wet AMD
Describe the visual changes with AMD and what an Amsler grid is
- blurred vision or scotomata
- Amsler grid: straight line grid but if it appears wavy, might have AMD
Tx for wet AMD
laser photocoagulation, photodynamic laser therapy, and intravitreal injection of VEGF inhibitors.
What can be done to help reduce a person’s risk for developing AMD?
- high doses of antioxidants such as vitamins E and C and zinc and beta-carotene
- spinach and kale
Recall where aqueous humor is made and how it is circulated and drained
- Ciliary body (where aqueous humor is made)
- Posterior chamber
- Iris
- Anterior chamber
- Trabecular network
- Canal of Schlemm
- Venous blood
Explain open angle and angle closure glaucoma.
- open angle: more common and caused by abnormalities in the trabecular meshwork that drains AH
- angle closure: caused by an obstruction of outflow of AH from the anterior chamber due to a narrow angle (more onset)(high IOP)
Describe the optic disc: optic cup ratio and how this suggests the possibility of increased IOP
-compares the diameter of the cup
portion with the diameter of the entire disc
-normal level is 1/3=.3
-glaucoma is 2/3=.6
Explain the mechanism of action for each of the treatment options listed for glaucoma
- beta 1 blockers: on ciliary body and increase aqueous humor
- cholinergic agonists: constrict pupil
- prostaglandin analogs: cause remodeling and widens space for aqueous humor to flow
- alpha agonists: inhibit aqueous humor production and constrict blood vessels to reduce AH productions
- Carbonic anhydrase inhibitors: reduces Cl- and associated water in the aqueous humor
clinical manifestations of an acute attack due to angle-closure glaucoma?
episodes of unilateral eye pain and headache, conjunctival redness, and blurred vision with halos around lights
Laser peripheral iridotomy
laser blasting away some of the trabecular network in order to widen the angle and relieve pressure
Explain how the ANS and lens and suspensory ligaments work to enable us to see far and near
- Tension on the suspensory ligaments by relaxed ciliary bodies put force on the lens to make more flat for distant vision
- Contracted ciliary bodies making suspensory ligaments slackened making the lens see more near sighted things
- ANS: sympathetic is more active for distance and parasympathetic is more active for near sighted vision
Understand the terms Myopia, Hyperopia and Presbyopia
- Myopia: “near sighted”, far is blurry
- Hyperopia: “far sighted”, close is blurry
- Presbyopia: loss of elasticity in the lens, hard to see things up close
Which lens is used to treat myopia and hyperopia?
- Myopia: concave, diverging lens (minus)
- Hyperopia: convex, converging lens (plus)
Explain what an astigmatism is
- blurry vision because of irregular shaped cornea or even lens
- bend light differently
- hard to correct vision
Explain what a cataract is
clouding of lens
What causes cataracts?
- due to aging as the lens protein fibers become damaged over time
- trauma, radiation, genetics, smoking, low vitamin C, diabetes
How are cataracts treated?
Surgery, artificial lens replaces old one
Pathway traveled for visual information
Beginning with visual fields
- Optic nerve
- Optic chiasm
- Optic tract
- Lateral geniculate nucleus (LGN)
- Optic radiations
- Visual cortex
Information from what portion of the visual field crosses over at the optic chiasm?
- right optic nerve leads to right eye blindness
- a lesion in the optic chiasm leads to bitemporal hemianopia
- a lesion in the left optic tract leads to bilateral right hemianopia
Explain how damage to the optic nerve causes anopsia
caused by infections, immune conditions that attack nerve tissue (like multiple sclerosis), trauma, glaucoma, and any diseases that affect the brain and central nervous system
Explain what tunnel vision is
and how it occurs and the other names for this condition
- vision is missing from the inner half of both right and left visual fields
- caused by: tumor that presses on the optic chiasma
Explain what homonymous
hemianopsia is and how it occurs
- a person can only see one side (right or left) of the visual field in each eye
- most common cause: stroke
What are the parts that make up the external, middle, and internal subdivisions of the ear?
- external ear: auricle, ear lobe, external acoustic meatus
- middle ear: tympanic membrane, ossicles
- inner ear: semicircular canals, cranial nerve VIII, cochlea, and Eustachian tube
What can cause otitis externa
infectious agents like Pseudomonas, E. coli and S. aureus
What are risk factors for development of otitis externa?
prolonged exposure to moisture
What are some manifestations of otitis externa?
inflammation and pruritus (itching) with tenderness and pain with earlobe retraction
What are common treatments for otitis externa?
eardrops that contain acidifying agents (acetic acid 5%), antimicrobials, and local anesthetics (benzocaine)
Give a description for acute otitis media. Describe the similarities and differences for AOM and OME
- Acute otitis media(AOM): rapid onset of signs and symptoms of a middle ear infection
- Otitis media with effusion(OME): inflammation of the middle ear and the presence of fluid but no signs or symptoms of an acute infection
In what age group does OM most commonly occur. List some risk factors for the development of OM
- Young children
- allergies or colds that can affect upper respiratory tract and increase congestion
What are some nonspecific signs and symptoms often observed in younger children with AOM
- otalgia (ear pain), fever and hearing loss
- create exudate behind the tympanic membrane, so it cannot vibrate well
What are tympanostomy tubes and what is their purpose?
- ventilation tubes or pressure equalization tubes
- put holes in tympanic membrane and placing small plastic tubes to allow for drainage of the fluid
Why might chronic otitis media cause speech and language delays?
conductive hearing loss, choleastomas, chronic mastoiditis and rare intracranial complications
Why might a tonsil and adenoidectomy help relieve otitis media?
Because tonsillitis can block eustachian tube
What is a cholesteatoma?
sloughed off epithelial cells that accumulate around the ear bones so they are unable to vibrate. leads to hearing loss
Symptoms for OME
hinting that brain structures are involved include persistent headaches, stiff neck, tinnitus, or cranial nerve disturbances (e.g., visual disturbances, facial paralysis)
What is Otosclerosis?
formation of new spongy bone around the stapes and oval window and results in progressive deafness due to immobilization of the middle ear bones
What is objective and subjective tinnitus? What are some causes for these two types of tinnitus?
- Objective: potentially detectable by another observer like turbulent blood flow due to vascular disorders
- Subjective: mechanism like cerumen, medications, noise induced hearing loss, HTN, atherosclerosis or a head injury
Describe the difference between conductive and sensorineural hearing loss
- Conductive: stimuli not conducted to the inner ear
- Sensorineural: stimuli failure to stimulate the inner ear or pathways that go to the brain
Describe how an infant might be tested for hearing using OAE and ABR.
- otoacoustic emission (OAE): sound that is generated by the cochlea. The outer hairs of the cochlea are tested with sound clicks.
- auditory brainstem evoked response(ABR): measuring EEG waves generated by the brain after applying a stimulus like tones or clicks to the hearing apparatus. They assess the neurons firing and the speed of transmission.
Describe what a cochlear implant is and how it works.
- small electronic device that has an external component and an internal component
- external: microphone
- internal: electrical current to the cochlea
