USMLE (Fach) / Ophthalmology, Otology (Lektion)
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- Cataract Painless, often bilateral, opacification of lens, often resulting in glare and ↓ vision, especially at night. Acquired risk factors:- ↑ age- smoking- excessive alcohol use- excessive sunlight- prolonged ...
- Glaucoma Optic disc atrophy with characteristic cupping (thinning of outer rim of optic nerve head), usually with elevated intraocular pressure (IOP) and progressive peripheral visual field loss. Open-angle ...
- Open-angle glaucoma - associated with ↑ age, African-American race, family history Primary: cause unclear Secondary: blocked trabecular meshwork from WBC (eg uveitis), RBC (eg vitreous hemorrhage), retinal elements (eg ...
- Closed-angle glaucoma Primary: enlargement or forward movement of lens against central iris --> obstruction of normal aqueous flow through pupil --> fluid builds up behind iris, pushing peripheral iris against cornea and impeding ...
- Conjunctivitis Inflammation of the conjunctiva → red eye Allergic – itchy eyes, bilateral Bacterial – pus; treat with antibiotics Viral – most common, often adenovirus; sparse mucous discharge, swollen preauricular ...
- Uveitis Inflammation of uvea, specific name based on location within affected eye. Anterior uveitis: iritisPosterior uveitis: choroiditis and/or retinitis - May have hypopyon (accumulation of pus in anterior ...
- Age-related macular degeneration Degeneration of macula (central area of retina).- Most common cause of blindness in individuals >65 in developed countries. Causes distortion (metamorphopsia, detected with Amsler grid) and eventual loss ...
- Diabetic retinopathy Retinal damage due to chronic hyperglycemia.- Most common cause of visual impairment and blindness in patients aged 24-75 in the US. Nonproliferative: damaged capillaries leak blood → lipids and fluid ...
- Retinal vein occlusion Blockage of central or branch retinal vein due to compression from nearby arterial atherosclerosis. Etiology:- Atherosclerosis, hypertension, diabetes mellitus- Hypercoagulable states: Polycythemia vera, ...
- Retinal detachment Separation of neurosensory layer of retina (photoreceptor layer with rods and cones) from outermost pigmented epithelium (normally shields excess light, supports retina) → degeneration of photoreceptors ...
- Central retinal artery occlusion Acute, painless monocular vision loss. - Retina cloudy with attenuated vessels and "cherry-red" spot at fovea (center of macula)- Grayish-white discoloration of entire retina - Evaluate for embolic source ...
- Retinitis pigmentosa Inherited retinal degeneration. Frequently mutation in the rhodopsin gene. - Early onset (5-30 years) - Painless, progressive vision loss beginning with night blindness (rods affected first). - Bone spicule-shaped ...
- Retinitis Retinal edema and necrosis leading to scar. - Often viral (HSV, CMV, VZV), but can be bacterial or parasitic. - May be associated with immunosuppression. - CMV retinitis is associated with a high rate ...
- Horner syndrome Sympathetic denervation of face →:- Ptosis (drooping of eyelid: superior tarsal muscle)- Anhidrosis (absence of sweating) and flushing of affected side- Miosis (pupil constriction) Associated with lesions ...
- CN III damage CN III has both motor (central) and parasympathetic (peripheral) components. Common causes include:- Ischemia → pupil sparing- Uncal herniation → coma- PCA aneurysm → sudden-onset headache- Cavernous ...
- Internuclear opthalmoplegia Medial longitudinal fasciculus (MLF): pair of tracts that allows for crosstalk between CN VI and CN III nuclei. Coordinates both eyes to move in same horizontal direction. Highly myelinated. Lesions may ...
- CN IV damage Eye moves upward, particularly with contralateral gaze. Problems going down stairs, may present with compensatory head tilt in the opposite direction.
- Miosis Constriction, parasympathetic 1st neuron: Edinger-Westphal nucleus to ciliary ganglion via CN III 2nd neuron: short ciliary nerves to pupillary sphincter muscles
- Mydriasis Dilation, sympathetic 1st neuron: hypothalamus to ciliospinal center of Budge (C8-T2) 2nd neuron: exit at T1 to superior cervical ganlion (travels along cervical sympathetic chain near lung apex, subclavian ...
- Auditory physiology Outer ear: Visible portion of ear (pinna), includes auditory canal and tympanic membrane. Transfers sound waves via vibration of tympanic membrane. Middle ear: Air-filled space with the three ossicles ...
- Diagnosing hearing loss Conductive hearing loss:Rinne: Abnormal (bone > air)Weber: Localizes to affected ear. Sensorineural hearing loss:Rinne: Normal (air > bone)Weber: Localizes to unaffected ear.
- Types of hearing loss Noise-induced hearing loss: Damage to stereociliated cells in the organ of Corti. Loss of high-frequency hearing first. Sudden extremely loud noises can produce hearing loss due to tympanic membrane rupture. ...
- Cholesteatoma Overgrowth of desquamated keratin debris within the middle ear space.Form a round, pearly mass behind the tympanic membrane in the middle ear. Primary cholesteatomas: Result of chronic negative pressure ...
- Vertigo Sensation of spinning while actually stationary. Subtype of "dizziness," but distinct from "lightheadedness." Peripheral vertigo: More common. Inner ear etiology (eg, semicircular canal debris, vestibular ...
- Refractive errors Hyperopia: Also known as "farsightedness." Eye too short for refractive power of cornea and lens → light focused behind retina. Correct with convex (converging) lenses. Myopia: Also known as "nearsightedness." ...
- Papilledema Optic disc swelling (usually bilateral) due to ↑ ICP (eg, 2° to mass effect). Etiology:- Hypertensive emergency- Idiopathic intracranial hypertension (eg, pseudotumor cerebri)- Intracranial tumores ...
- Pupillary control Miosis: Constriction, parasympathetic- 1st neuron: Edinger-Westphal nucleus to ciliary ganglion via CN III- 2nd neuron: short ciliary nerves to sphincter pupillae muscles (M3) Pupillary light reflex:- ...
- Marcus Gunn pupil = Relative afferent pupillary defect When the light shines into a normal eye, constriction of the ipsilateral (direct reflex) and contralateral eye (consensual reflex) is observed. When the light is ...
- Cavernous sinus Collection of venous sinuses on either side of pituitary. Blood from eye and superficial cortex → cavernous sinus → internal jugular vein. CNs III, IV, V1, VI, and occasionally V2 plus postganglionic ...
- Aqueous humor pathway Produced by nonpigmented epithelium on ciliary body (↓ by β-blockers, α2-agonists, and carbonic anhydrase inhibitors). Trabecular outflow (90%): Drainage through trabecular meshwork → canal of ...
- Hypertensive retinopathy Retinal damage due to chronic uncontrolled HTN. - Flame-shaped retinal hemorrhages- Arteriovenous nicking (the arteriole's thick arteriosclerotic wall compresses the vein where it crosses, so that the ...
- Ocular motility CN VI innervates the lateral rectus:CN IV innervated the superior oblique.CN III innervates the rest. The strongest action of the superior oblique is depression when the eye is adducted. The further the ...
- Argyll Robertson pupil - No direct or consensual light reflex - Accomodation-convergence intact - Seen in neurosyphilis, diabetes
- Visual field defects 1. Right anopia (optic nerve)2. Bitemporal hemianopia (pituitary lesion, optic chiasm)3. Left homonymous hemianopia (optic tract)4. Left upper quadrantanopia (Meyer loop, right temporal lesion, MCA)5. ...
- Ménière disease Cause: Increased pressure & volume of endolymph due to impaired resorption of endolymphatic fluid. Features:Traid: Vertigo, hearing loss, tinnitus- Ear fullness/pain- Episodes last minutes to hours- Sensorineural, ...
- Benign paroxysmal positional vertigo Disease of the inner ear caused by small particles (otoliths) dislodging and migrating within the endolymphatic fluid into one of the semicircular canals. Features:- Brief episodes brought on by head ...
- Vestibular neuritis (labyrinthitis) Acute unilateral vestibulopathy due to inflammation of vestibular nerve (viral or postviral). Features:- Single episode that can last days- Severe vertigo with falling towards the affected side- No hearing ...