Special Senses Flashcards
Function of outer ear
Transfer sound waves via ear drum
Bones of middle ear
Ossicles: Malleus, Incus, Stapes
Function of ossicles
Amplify sound from eardrum to inner ear
Structure that contains basilar membrane
Cochlea
Area of inner ear that best detects low frequency sounds
Apex of basilar membrane near helicotrema
Area of inner ear that best detects high frequency sounds
Base of cochlea
Location of tuning fork in Rinne test
Next to ear
Purpose of Rinne test
Test for conductive hearing loss
Abnormal Rinne test for conductive hearing loss
Bone conduction > Air conduction
Location of tuning fork in Weber test
On top of head
Purpose of Weber test
Localizes
Abnormal Weber test for sensorineural hearing loss
Sound localizes to good ear
Normal Rinne test
Air conduction > Bone conduction
Abnormal Weber test for conductive hearing loss
Sound localizes to bad ear
Normal Weber test
Sound heard equally in both ears
Aging related sensorineural hearing loss
Presbycusis
Mechanism of presbycusis
Destruction of hair cells at cochlear base
Overgrowth of desquamated keratin debris within middle ear space leading to conductive hearing loss
Cholesteatoma
Sensation of spinning while actually standing
Vertigo
Types of vertigo
Peripheral and Central
Etiology of peripheral vertigo
Inner ear defect
Etiology of central vertigo
Brain stem or cerebellar lesion
Which type of vertigo is more common
Peripheral
Causes of peripheral vertigo
Semicircular canal debris, vestibular nerve infection, Meniere disease, benign paroxysmal positional vertigo
Findings in central vertigo
Directional or vertical nystagmus, skew deviation, diplopia, dysmetria
Positional testing results in central vertigo
Immediate nystagmus in any direction, focal neurologic findings
Positional testing results in peripheral vertigo
delayed horizontal nystagmus
Outer layer of the eye
Sclera
Middle layer of the eye
Choroid
Inner layer of the eye
Retina
Structures within the optic canal
Optic nerve, central retinal vein and artery
Most common cause of conjunctivitis
Viral (adenovirus)
Presentation of viral conjunctivitis
Sparse mucus discharge and swollen preauricular lymph nodes
Treatment for bacterial conjunctivitis
Antibiotics
Presentation of allergic conjunctivitis
Bilateral itchy eyes
Presentation of bacterial conjunctivitis
Pus from infected eye
Where is light focused in relation to retina in hyperopia
Behind retina
Farsightedness
Hyperopia
Type corrective lens needed for hyperopia
Convex (converging) lens
Nearsightedness
Myopia
Type corrective lens needed for myopia
Concave (diverging) lens
Where is light focused in relation to retina in myopia
In front of retina
Abnormal curvature of cornea
Astigmatism
Type of corrective lens needed for astigmatism
Cylindrical lens
Aging-related impaired accommodation of lens
Presbyopia
Mechanism of presbyopia
Decreased elasticity of lens and strength of ciliary muscle and changes in lens curvature
Painless, often bilateral opacification of lens resulting in decreased vision
Cataracts
Trabecular outflow for Aqueous humor
Drains through:
- trabecular meshwork
- canal of Schlemm
- episcleral vasculature
Site of aqueous humor synthesis
Ciliary body
Drugs that decrease aqueous humor production
Beta blockers, alpha2-agonists and carbonic anhydrase inhibitors
Drugs that increase trabecular outflow of aqueous humor
M3 agonists
Drugs that increase uveoscleral outflow of aqueous humor
Prostaglandin agonists
Muscles that make up the iris
Dilator muscle (alpha-2) Sphincter muscle (M3)
Receptors found on dilator muscle of the iris
Alpha-2 receptors
Receptors found on sphincter muscle of the iris
M-3 receptors
What effects lens shape for accommodation
Ciliary body muscle fibers
What suspends lens from ciliary body
Zonule fibers
Optic disc atrophy with cupping
Glaucoma
Cause of glaucoma
Increased intraocular pressure (IOP)
Consequence of untreated glaucoma
Progressive peripheral visual field loss
Type of glaucoma more common in African-Americans secondary to blocked trabecular meshwork
Open-angle glaucoma
What is contraindicated in patient presenting with very painful, red eye, sudden vision loss, halos around lights, frontal headache with fixed and mid-dilated pupils
Epinephrine (has acute closed angle glaucoma)
Presentation of chronic closed angle glaucoma
Often asymptomatic with damage to optic nerve and peripheral vision
Mechanism of primary closed angle glaucoma
Enlargement or forward movement of lens against central iris
Treatment for Dry age-related macular degeneration
Multivitamin and antioxidant supplements
Treatment for Wet age-related macular degeneration
Ranibizumab injections (anti-VEGF)
Most common type of age-related macular degeneration
Dry (non-exudative)
Mechanism of Dry age-related macular degeneration
Deposition of yellowish extracellular material between Bruch membrane and retinal pigment epithelium
Mechanism for Wet age-related macular degeneration
Rapid loss of vision due to bleeding secondary to choroidal neovascularization
Retinal damage due to chronic hyperglycemia
Diabetic retinopathy
Types of diabetic retinopathy
Non-proliferative and proliferative
Mechanism for proliferative diabetic retinopathy
Chronic hypoxia causes angiogenesis resulting in traction on retina
Mechanism for non-proliferative diabetic retinopathy
Leaky capillaries cause lipids and fluid to seep into retina resulting in hemorrhages and macular edema
Treatment for proliferative diabetic retinopathy
Peripheral retinal photocoagulation, surgery, anti-VEGF
Treatment for non-proliferative diabetic retinopathy
Blood sugar control
Mechanism of retinal vein occlusion
Blocked central or branch retinal vein from nearby arterial atherosclerosis
Separation of neurosensory layer of retina from outermost pigmented epithelium
Retinal detachment
Consequence of retinal detachment
Degeneration of photoreceptors leading to vision loss
Retinal detachment findings on fundoscopy
Crinkling of retinal tissue and changes in vessel direction
Eye condition presenting with acute painless mononuclear vision loss and cloudy retina with attenuated vessels and cherry-red spot on fovea
Central retinal artery occlusion
What is needs to be done next once diagnosis of central retinal artery occlusion is made?
Evaluate for embolic source
Inherited retinal degeneration presenting with painless, progressive vison loss beginning with night blindness and bony spicule pattern around macula
Retinitis pigmentosa
Retinal edema and necrosis leading to scar; often viral but bacterial also; associated with immunosuppression
Retinitis
Bilateral optic disc swelling from increased ICP with enlarged blind spot and elevated optic disc with blurred vision
Papilledema
Parasympathetic constriction of eyes
Miosis
Control of miosis
1st neuron: Edinger-Westphal nucleus to ciliary ganglion via CN III
2nd neuron: short ciliary nerves to sphincter muscles
Pupillary light reflex
Light enter retina, enters CN III to Pretectal nuclei in midbrain, activating both Edinger-Westphal nuclei causing consensual constriction
Sympathetic dilation of eyes
Mydriasis
Mydriasis pathway
1st neuron: hypothalamus to ciliospinal center of Budge (C8-T2)
2nd neuron: exits at T1 to superior ganglion
3rd neuron: plexus along internal carotid to cavernous sinus entering orbit as ciliary nerve to pupillary dilators
Afferent pupillary defect from optic nerve damage decreasing pupillary constriction when light is shone in bad eye relative to good eye
Marcus Gunn pupil
Sympathetic denervation of face causing ptosis, miosis, anhydrosis associated with lesions above T1 or Pancoast tumors
Horner syndrome
Action of superior oblique
Abducts, intorts and depresses adducted eye
Position of superior and inferior obliques when tested
Adducted
Motor signs with CN III damage
Ptosis and “down-and-out” gaze
Parasympathetic signs with CN III damage
Diminished or absent pupillary light reflex, “blown pupil” often with “down-and-out” gaze
Motor signs with CN IV damage
Eye moves upward with contralateral gaze
Motor signs with CN VI damage
Medially directed eye that cannot abduct
Visual field deficit with damage to optic nerve
Ipsilateral whole field (right anopia)
Visual field deficit with damage to optic chiasm
Temporal both eyes (bitemporal hemianopia)
Visual field deficit with damage to optic tract
Temporal contralateral eye/Nasal ipsilateral eye (homonymous hemianopia)
Visual field deficit with damage to temporal lobe (Meyer loop)
Upper: temporal contralateral/nasal ipsilateral (upper quadrantanopsia)
Visual field deficit with damage to parietal lobe
Lower: temporal contralateral/nasal ipsilateral (lower quadrantanopsia)
Lesion in MLF leads to what disorder
Internuclear ophthalmoplegia
MLF function
Connects CN III to CN VI to coordinate horizontal eye movements