Lec 26 Visual System and Gaze Disorders Flashcards
What are the 3 layers of the eye?
external: sclera and cornea
intermediate: iris, ciliary body, choroid
internal: retina
What is the iris?
circular pigmented membrane enclosing pupil
What is the ciliary body?
just beneath sclera + lateral to lens
makes aqueous humor
contains ciliary muscle that allows lens to change shape to focus
What is the choroid?
layer of connective tissue and blood vessels between sclera and retina
suplles nutrients to the eye
What are the three fluid compartments of the eye?
- anterior and posterior chambers in front of lens [separated by iris]
- vitreous body [between back of lens and retina, contains jelly-like substance
What do the anterior/posterior chambers of eye contain?
aqueoue humor
What is an example of aqueous humor disorder?
glaucoma [excess aqueous humor in eye from drainage obstruction and other causes]
What is the lens?
biconvex structure, refracts light to focus it on retina
What is blood supply to lens?
avascular
What suspends the lens? what happens to these over time?
- zonules
- they weaken with advanced age which is what causes eye problems as you get older
What are two examples of lens disorders?
presbyopia
cataracts
what is presbyopia?
loss of ability of lens to change shape [focus between distance and near]
– occurs with age, lens hardens and less elastic
what are cataracts?
clouding/yellowing of lens with advanced age
- initially have mild disturbance of vision then progressive loss
What is glaucoma?
excess aqueous humor (over production, under drain)
causes increased pressure thus lead to optic nerve injury and decreased vision
What are clinical signs of glaucoma?
- high IOP
- cupping of optic nerve
- peripheral visual field loss progressing inward
What are two types of glaucoma?
- primary open angle
- closed angle
What is primary open angle glaucoma?
- wide/open angle betwen iris and cornea
- due to slow clogging of drainage canals of eye
- asymptomatic early but can advance to irreversible vision loss
- most common type in elderly
What is closed angle glaucoma?
- less common
- higher risk in asians, females, hyperopia
- angle/drainage canal between iris + cornea closed or narrow
- creates suddent rise in IOP –> need meds or laser surgery
- signs: ocular pain, redness, N/V, headche, blurred vision, halos around light
What is age-related macular degeneration [ARMD]? risk factors?
ARMD = degenerative disease of macula/fovea –> get decreased central vision/blind spot
risk factors: age > 70, fair skin, family history, smoking, heart disease
What are the two types of ARMD?
- wet and dry
What is dry ARMD? signs?
- gradual visual loss due to formation of small yellow deposits under macula
- early = asymptomatic, straight lines appear crooked, advanced = central blind spot
What are drusen?
small yellow deposits under macula, cause dry ARMD
What is wet ARMD?
- sudden, severe visual loss due to growth of blood vessels + bleeding under retina
decrease risk: eat fruits/veggies
What is diabetic retinopathy?
- increased blood glucose damages retinal capillaries –> breakdown blood retinal barrier
- causes retinal ischemia
what are findings of diabetic retinopathy?
- early = asymptomatic
- may have microaneurysms, hard exudates, intraretinal hemmorrhage
- cotton wool spots
- retinal ischemia
what are the 3 clinical stages of diabetic retinopathy
non-proliferative: asymptomatic
pre-proliferative: give laser therapy to prevent long term vision loss
proliferative: major cause severe visual loss, need laser treat or surgery
what is treatment for severe diabetic retinopathy? side effects?
- kill off peripheral ganglion skills to prevent VEGF from forming
- laser treatment (causes some loss of peripheral vision and decreased night vision)
How does hyperglycemia affect eyes?
when blood glucose > 200, lens can swell in eye and lead to blurred vision
How does retinal detachment present?
- presents with: light flashes due to tugging of vitreous on retina, floaters, curtain over vision, can create whole in retina
- usually have symptoms before retinal detachment
What is a retinal infarct? signs?
central retinal artery occlusion
–> see retinal whitening/edema and cherry red spot in the middle
if not treated w/in 3 hrs –> permanent vision lost
What is hollenhorst plaque?
thromboembolus in retinal arteriole
what is retinitis pigmentosa? signs?
- disorder of rods that involves progressive retinal degeneration due to pigmentary depositis
- also see optic nerve atrophy
- symptoms: nigh/low vision blindness, tunnel vision
- slow process takes decade to happen
- may be hereditary
What is a roth spot? what 2 systemic diagnoses should you consider?
- retinal hemorrhage with white center
- infective endocarditis
- leukemia
What covers the optic nerve?
meninges! because its just an extension of the CNS
What is optic neuritis? pathogenesis?
- inflammatory optic neuropathy
- presumed to be due to demyelination
What disease are associated with optic neuritis?
- multiple sclerosis
- sarcoidosis
- neuromyelitis optica
- infections
Who gets optic neuritis?
usually under age 40
What are symptoms of otpic neuritis?
- acute onset: unilateral loss of visual acuity, color, field
- pain on eye movement
- may or may not have afferent pupillary defect [APD]
- on exam: optic nerve head swollen or normal
- visual loss worst days - 2 wks after onset, recover over wks - months
24 yo comes in with blurry vision, one eye really hurts with movement?
think optic neuritis!
What is treatment optic neuritis typically?
- can resolve on its own after wks to months
- to accelerate: give IV steroids
- give MRI since there is an association with MS
What is typical of MS on MRI of brain?
white matter periventricular lesions > 3mm in size
What is risk of MS with optic neuritis?
22%
or 72% if any sort of periventricular white matter lesion
What is papilledema?
optic disc edema/swelling caused by high intracranial pressure, usually bilateral
- optic disc edema without ICP is not papilledema
What are causes of bilateral optic disc edema?
- papilledema
- malignant hypertension
- ischemia/inflamation, etc
What are causes of papilledema?
- intracranial mass [frontal lobe meningioma
- hydrocephalus
- pseudotumor cerebri
What is mech of optic disc edema?
lack of axonal transport from build up of pressure greater than IOP –> get disc swelling
What are symptoms of papilledema?
- many nerve axons lost before any detectable visual field defect
- once visual loss begins, rapidly progresses
- get chronic to atrophic papilledema within 3 wks
Which muscle contraction leads to miosis? which mydriasis?
sphinter = miosis [PNS]
dilator muscle = mydriasis [SNS]
What is physiologic anisocoria?
unequal pupil size
what is relative afferent pupillary defec [APD]t? test?
- defect = if input from one eye is less than the other
- swinging flashlight test –> input from one eye is less than other eye
causes of APD?
- optic neuritis/glaucoma
- chiasmal or optic tract lesion
- severe retinal damage
- amaurotic pupil
NOT: ocular media opacities [cataract] or amblyopia
What is Holmes-Adie’s Tonic Pupil?
- idiopathic
- one pupil abnormally large –> constricts poorly to light, due to palsy of iris sphincter muscle
What is horner syndrome? signs?
oculosympathetic paralysis on one side
- could indicate dissection of carotid artery
signs:
- ptosis and small pupil on one side
- anhidrosis [decreased sweating] of the affected forehead
- enesecoria worse in the dark [eye doesn’t dilate in the dark]
who is at risk for glaucoma?
- elderly
- afica americans
- people with elevated intraocular pressure
- family history of glaucoma
What should you think if pt presents with: gradual vision loss startig at periphery and progressing in?
glaucoma = tunnel vision
What should you think it pt presents with: vision loss starting with central blind spot in elderly
age-related macular degenration [ARMD]
What should you think: pt says straight lines appear crooked?
dry ARMD
Is dry or wet ARMD more gradual?
dry!
Should type 1 or type 2 diabetes have annual opthalmologic exams immediately after diagnosis?
type 2 because its likely they were undetected or had high blood glucose for a while
What is leading cause of blindness in working age americans?
diabetic retinopathy
What are argyll robertson pupils?
- bilateral
- dissociation of light-near reflexes
- irregular pupils, accomodate [constrict in near] but don’t react [constrict in lihgt]
What are some possible common causes of argyll robertson?
- neurosyphilis
- diabetes
What are signs of pupil defect associated with 3rd nerve palsy?
- mydriasis [dilation]
- ptosis
- can’t react to light or near
What is common cause of CN3 pupil lesion? why is pupil vulnerable?
- fibers to pupil are external part of nerve = vulnerable to compression
- common cause = aneurysm of posterior communicating artery (Pcom)
