Rubin's 33: The Eye Flashcards
blowout fracture
Blunt trauma increases intraorbital pressure momentarily and may cause the bones in the floor of the orbit to fracture into the maxillary sinus
enophthalmos
The inferior rectus muscle may become entrapped in a blowout fracture, thereby causing the eye to sink into the orbit
siderosis bulbi
retinal degeneration and discoloration of the eye from iron
Blepharitis
inflammation of the eyelids. It is common and sometimes produces an acute, red, tender, inflammatory mass.
Hordeolum (sty)
an acute, inflammatory, focal lesion of the eyelid
- Acute inflammation involving the meibomian glands is termed an INTERNAL hordeolum
- acute folliculitis of the glands of Zeis is an EXTERNAL hordeolum.
Chalazion
- granulomatous inflammation centered around the meibomian glands or the glands of Zeis
- a reaction to extruded lipid secretions, usually produces a painless swelling in the eyelid
Xanthelasma
a yellow plaque of lipid-containing macrophages, usually involving the nasal aspect of the eyelids.
- often seen in older persons and patients with disorders of lipid metabolism
exophthalmos
bilateral abnormal forward extrusion of the eyeball
proptosis
unilateral abnormal forward extrusion of the eyeball
What happens to the eye in Graves disease?
Exophthalmos,may precede or follow other manifestations of thyroid dysfunction
- occurs in early adult life, especially in women (female-to-male ratio, 4:1)
- may be severe and progressive, particularly in middle life, when exophthalmos no longer correlates well with the state of thyroid function.
- edema of the eyelids, chemosis (conjunctival edema) and limitation of ocular motion
Inflammatory pseudotumor
- a chronic idiopathic inflammatory condition associated with a variable degree of fibrosis
- a common cause of proptosis and partial immobility of the eyeball
Conjunctival hemorrhage
- may result from blunt trauma, anoxia, severe coughing, or spontaneously
- does NOT spread into the cornea because of the barrier imposed by the close apposition of corneal epithelium to the underlying substantia propria
conjunctivitis
- may be allergic or infectious
- infectious caused by microorganism lodging on the surface of the eye or by hematogenous spread
- iatrogenic infxns may follow ophthalmic manipulations, such as corneal grafts, intraocular implantation of lens prostheses or use of infected eyedrops or diagnostic instruments
- hyperemic conjunctival blood vessels
- inflammatory exudate that accumulates in the conjunctival sac commonly crusts, causing the eyelids to stick together in the morning. May be purulent, fibrinous, serous or hemorrhagic
trachoma
- a chronic, contagious conjunctivitis caused by Chlamydia trachomatis
- virtually always bilateral and involves the upper half of the conjunctiva more than the lower
- cellular infiltrate is predominantly lymphocytic, and conjunctival lymph follicles with necrotic germinal centers are characteristic.
- lymphocytes and blood vessels invade the superior portion of the cornea between the epithelium and Bowman zone.
- Scarring of the conjunctiva and eyelids distorts the eyelids.
- On microscopic examination, the desquamated conjunctival epithelium exhibits glycogen-rich intracytoplasmic inclusion bodies and large macrophages containing nuclear fragments (Leber cells). Secondary bacterial infections occur commonly.
inclusion blennorrhea
- a purulent conjunctiviti that develops in newborns, who become infected during passage through the birth canal.
- also acquired by swimming in nonchlorinated pools or from contact with dis- charges of infected urethra or cervix.
inclusion conjunctivitis
- follicular conjunctivitis with focal lymphoid hyperpla- sia caused by Chlamydia in older children and adults
- in contrast to trachoma, the lower tarsal conjunctiva is involved
- Scarring and necrosis do not develop, and keratitis is rare and mild.
Ophthalmia neonatorum
- severe, acute conjunctivitis with a copious purulent discharge, especially in the newborn, caused by Neisseria gonorrhoeae.
- complicated by corneal ulceration, perforation, scarring and panophthalmitis.
- treated with 5% Betadine eye drops.
Pinguecula
a yellowish conjunctival lump usually located nasal to the corneoscleral limbus.
- MC conjunctival lump, consists of sun-damaged connective tissue
Pterygium
- a fold of vascularized conjunctiva that grows horizontally onto the cornea in the shape of an insect wing
- often associated with a pinguecula and frequently recurs after excision.
HSV difference in primary ifxn and reactivation
Primary infxn:
- subclinical or undiagnosed localized ocular lesions are caused by HSV type 1 in childhood.
- accompanied by regional lymphadenopathy, systemic infection and fever.
- Most corneal lesions due to HSV are asymptomatic plaques of diseased epithelial cells that contain replicating virus.
- usually heal without ulceration, but an acute unilateral follicular conjunctivitis may occur. Corneal ulcers appear after serum antibody levels increase.
Reactivation of latent infxn:
- Unlike primary HSV infection, reactivation disease is characterized by corneal ulceration and a more severe inflammatory reaction.
- may be precipitated by ultraviolet light, trauma, menstruation, emotional and physical stress, exposure to light or sunlight, vaccination and other factors
HSV lesions in primary infxn
- multiple, minute, discrete, intraepithelial corneal ulcers (superficial punctate keratopathy).
- some of these lesions heal, others enlarge and eventually coalesce to form linear or branching fissures (dendritic ulcers).
- The epithelium between the fissures desquamates, leading to sharply demarcated, irregular geographical ulcers
How are HSV ulcers visualized?
Fluorescin
HSV lesions in secondary infxn
- central disc-shaped corneal opacity develops beneath the epithelium, owing to edema and minimal inflammation (disciform keratitis)
- thinning of corneal stroma, Descemet membrane may bulge into it (descemetocele)
- Corneal perforation can also occur.
Onchocerciasis
- caused by parasite
- accounts for blindness in at least half a million people in regions of Africa and Latin America in which it is endemic.
- Microfilariae released from fertilized adult female worms migrate into the superficial cornea, bulbar conjunctiva, aqueous humor and other ocular tissues.
- intracorneal microfilariae die and elicit an inflammatory response that leads to corneal opacification and visual impairment (river blindness).
- Tx: ivermectin
annulus lipoides
- frequent in the elderly
- accompanies certain disorders of lipid metabolism
Arcus Lipoides
a white arc due to lipid deposition in the peripheral cornea
Band Keratopathy
- an opaque horizontal band across the cornea
- may contain calcium phosphate (calcific band keratopathy) or noncalcified protein (chronic actinic keratopathy)
calcific band keratopathy
- calcium phosphate deposits in a horizontal band across the superficial central cornea in conditions associated with hypercalcemia
- most often occurs in the absence of hypercalcemia, as in chronic uveitis.
Chronic actinic keratopathy
- most severe in regions in which people spend a consider- able amount of time outdoors
- unprotected eyes are exposed to excessive ultraviolet light, such as that reflected from desert, water or snow.
Meesmann dystrophy
- epithelial dystrophy caused by dominant mutations in the KRT3 or KRT12 genes, which encode keratin 3 and keratin 12, respectively
- result in aggregations of abnormal cytokeratin filaments and severely impair cytoskeletal function in the affected cells
familial subepithelial corneal dystrophy
- AR bilateral epithelial dystrophy where the TACSTD2 gene is mutated
- amyloid is found beneath the corneal epithelium in gelatinous drop-like deposits
macular corneal dystrophy
a defect in the CHST6 gene, which encodes a sulfotransferase that catalyzes sulfation of N-acetyl glucosamine and galactose in keratan sulfate
Genes implicated in stromal dystrophies
- TFGBI (many)
- CHST6 (macular corneal dystrophy)
- PIP5K3 (fleck corneal dystrophy)
- DCN (congenital stromal corneal dystrophy)
- UBIAD1 (Schnyder corneal dystrophy)
Fuchs endothelial corneal dystrophy
- wartlike excrescences form on the Descemet membrane (guttae), and progressive visual loss follows corneal edema and endothelial cell degeneration
- missense mutations in COL8A2 (encodes the α2-chain of type VIII collagen)
cataracts
- opacifications in the crystalline lens
- causes: old age, diabetes, nutritional deficiencies, toxins, drugs, physical agents
- may develop in ocular diseases such as uveitis, intraocular neoplasms, glaucoma, retinitis pigmentosa and retinal detachment
- congenital rubella virus infection, some skin diseases, various systemic diseases
What happens in the development of cataracts?
- clefts appear between the lens fibers, degenerated lens material accumulates in these spaces
- Degenerated lens material exerts osmotic pressure, causing the damaged lens to imbibe water and swell, obstructing the pupil and causing glaucoma (phacomorphic glaucoma)
What happens in a mature cataract?
- entire lens degenerates, and the lenticular debris escapes into the aqueous humor through the lens capsule, diminishing the volume of the lens
- the extruded lenticular material is engulfed by macrophages and may obstruct aqueous outflow and produce glaucoma (phacolytic glaucoma)
- compressed lens fibers in the center of the lens normally harden with aging (simple nuclear sclerotic cataract) and may become brown or black
- If the peripheral part of the lens becomes liquefied (morgagnian cataract), the sclerotic nucleus may sink within the lens by gravity
Presbyopia
- a failure of accommodation due to aging
- the near point of distinct vision becomes located farther from the eye
- displacement of lenticular fibers causes loss of elasticity so lens can’t become spherical –> accomodation is shitty
Phacoanaphylactic dndophthalmitis
- an autoimmune granulomatous reaction to lens proteins
- an inflammatory lesion occurs around or within the lens (or its remains) in an eye with a traumatized or cataractous lens and sometimes after surgical removal of a cataractous lens
- similar reaction may occur spontaneously in the contralateral eye months or years later.