thyroid pathology - university of minnesota duluthjfitzake/lectures/dmed/vision/othersnotes/... ·...

eye infections

Lecture informationLecturerKristine Krafts, M.D.Elvis-obsessed.Veni, vidi, volo in domum redire.*

Outline Introduction Orbit Eyelid Conjunctiva Cornea Retina

* I came, I saw, I want to go home.

eye infections | 2 of 11

Introduction Eye anatomy

Robbins, fig. 29-1

How to think about an eye infection1. By anatomic compartment.2. By age of patient.3. By offending bug.4. Remember: not every inflammatory process in the eye is caused by an organism!1

Clinical termsblepharitis inflammation of eyelidchalazion lipogranuloma at eyelid margin (from an obstructed sebaceous gland which leaks lipids into surrounding tissue) chorioretinitis inflammation of the retina extending into the choroidconjunctivitis inflammation of the conjunctivadacryocystitis inflammation of lacrimal sac endophthalmitis inflammation within the vitreous humorepiscleritis inflammation of the sclerahordeolum focal inflammation of eyelid margin (also called stye)hypopyon pus in the anterior chamberkeratitis inflammation of the corneakeratoconjunctivitis extensive inflammation of conjunctiva and cornea

1 Lots of things besides bugs can cause inflammation: chronic diseases like rheumatoid arthritis, allergic diseases, neoplasms, you name it.

intro | orbit | eyelid | conjunctiva | cornea | uvea | retina


ophthalmia neonatorum conjunctivitis in neonatepanophthalmitis inflammation of retina, choroid, sclera, and orbituveitis inflammation of uveal tract (iris, ciliary body, choroid)Infectious agentsBacteriaStaphylococcus aureus gram-positive cocci in clusters catalase positive, coagulase positive part of normal flora of skin, noseStreptococcus pneumoniae gram positive diplococci catalase negative alpha-hemolytic encapsulatedPropionibacterium acnes gram-positive rod causes acneNeisseria gonorrhoeae gram-negative diplococcus oxidase positive common STDHaemophilus influenzae gram-negative rod fastidious organism (to culture H. influenzae, need

to use chocolate agar, which has X and V factors in it)Chlamydia trachomatis obligate intracellular bacterium (can't make own

ATP) too small to be seen on gram stain "elementary body" – infective form (sporelike,

extracellular structure) "reticulate body" – replicating form (intracellular) very common – and often undiagnosed – sexually-

transmitted disease (STD) can't diagnose on gram stain – so, look for Chlamydia

antigen (in serum) or do a conjunctival scraping and stain it with Papanicolou stain (to look for characteristic chlamydial inclusions – really just enlarged endosomes!)

Pseudomonas aeruginosa gram-negative rod oxidase positive smells fruity (in lab, and sometimes in patient!) may make pigments (e.g., fluorescein) – pus may be

fluorescent (or, under regular room light, may look bluish) ubiquitous (lives in soil and water) often drug-resistant


chlamydial inclusions(Pap stain)

Staphylococcus aureus

cocci in clusters


Mycobacterium tuberculosis and avium gram-positive rod hard to stain with gram stain because of waxy cell

wall! Acid-fast stains work. M. tuberculosis causes tuberculosis (no, really?) M. avium infection is more common in already-

immunocompromised patients (like patients with AIDS)

FungiMucor one of a group of fungi known as zygomycetes broad, ribbon-like, branching hyphae with almost no septae ubiquitous: soil, bread. devastatingly destructive in immunocompromised patientsCandida dimorphic fungus: (1) yeast (little round

things) and (2) hyphae (including both true hyphae and pseudohyphae, which are long buds that look like hyphae).

part of normal skin, mucous membrane flora some species are drug-resistantAspergillus branching, septate hyphae usual site of infection: lung destructive (grows right through blood

vessels)Pneumocystis carinii Little cup-shaped organisms Common in immunocompromised patients (especially

patients with AIDS) Usual site of infection: lung

VirusesAdenovirus double stranded DNA virus family: Adenoviridae usual diseases: upper and lower respiratory

tract infections, diarrhea, conjunctivitis diagnosis: tissue cultureCytomegalovirus double stranded DNA virus family: Herpesviridae usual disease: Cytomegalic inclusion disease infected cells are big, and show a big pink

nuclear inclusion and smaller basophilic cytoplasmic inclusions


mucorribbon-like

hyphae

candidayeasts and hyphae

CMV in lungintranuclear and cytopasmic

inclusionseye infections | 5 of 11

diagnosis: tissue culture, characteristic inclusions in cells

Herpes simplex virus double stranded DNA virus family: Herpesviridae usual diseases: cold sores, genital herpes infected cells are big, and show big intranuclear

inclusions surrounded by clear halos diagnosis: tissue culture, characteristic

inclusions in cells

ParasitesAcanthamoeba amoeba found in soil and water organism infects cornea and sometimes brain prolonged course; usually fatalOnchocerca volvulus nematode endemic areas: Africa, South America, Yemen vector: black fly disease (river blindness) involves chronic pruritic

dermatitis and blindnessTrichinella spirosis nematode uncommon in US now because of strict laws

requiring cooking of hog food transmitted through ingestion of raw, contaminated

pork (pigs get infected by eating infected rats or pork food products)

organisms love striated muscle (including the extraocular muscles), but also infect the heart and the CNS.

organisms often evoke marked eosinophilia.Trypanosoma cruzi protozoan endemic area: South America (rarely occurs in US,

Mexico) transmitted by "kissing bug" that hides in cracks of

loosely constructed houses bug bites sleeping inhabitant and leaves little

infectious poopy nearby human scratches bite and infected poopy gets inside



organisms cause cardiac and sometimes gastrointestinal damage.

Toxoplasma gondii protozoan definitive host: cat; intermediate hosts: humans, other

animals transmitted through ingestion of raw, contaminated

meat or through exposure to contaminated cat feces. disease can be congenital (malformations,

chorioretinitis, stillbirth), infectious-mono-like (chills, fever, headache, lymphadenopathy), or disseminated in immunocompromised patients (pneumonitis, myocarditis, and encephalitis)

How to make a diagnosis Look at conjunctiva, sclera (red? edematous?

discharge?) Look at exudate (if there is one): pus (with PMNs) in

bacterial infections, more watery (with lymphocytes) in viral infections, very watery (with eosinophils) in allergic reactions.

Slit-lamp examination (to get a good, magnified look inside eye)

Corneal scrapings for gram stain, fungal stains, bacterial/fungal/viral culture.

Deeper infections require special techniques (e.g., removal of vitreous humor)

Serology and blood cultures are occasionally helpful (in systemic diseases like Toxoplasmosis and Candida sepsis)


Trypanosoma cruzi


OrbitOrbital cellulitisOrganisms Typical oral/nasopharyngeal flora (e.g.,

Staphylococci) MucorDisease Because of the proximity of the sinuses to the orbit,

uncontrolled sinus infections may spread to the orbit. The most devastating of these is mucormycosis, an

uncommon rhinocerebral infection which occurs in patients with malignancies or diabetes

Mucor is very invasive: goes right through sinuses to eyes and brain. It is rapidly fatal – so need to diagnose and treat quickly.

Diagnosis tissue biopsy cultures sometimes negative!


The orbit is just above the maxillary sinus and just lateral to the ethmoidal sinus.

Mucormycosis in a man with diabetes


EyelidStyes Organisms: Staphylococcus aureus,

Propionibacterium acnes Disease: infection of glands at base of eyelid

causing a hot, red, painful nodule. Treatment: warm packs, topical antibiotics if

necessary.

Weird stuffTrichinosis Organism: Trichinella spirosis Transmission: eating raw pork Symptoms: bilateral lid swellingChagas disease Organism: Trypanosoma cruzi Endemic areas: Central and South America Transmission: Reduviidae ("kissing") bug, infected

with T. cruzi, bites human on face then turns around and chagas right on the bite; human scratches infected T. cruzi poopy into skin/eye.

Symptoms: unilateral lid swelling


Styes are usually caused by Staph aureus and are treated with hot packs.

stye


ConjunctivaNeonatal conjunctivitisOrganisms Chlamydia trachomatis (serotypes D-K) Neisseria gonorrhoeae Staphylococcus aureusTransmission passage through infected birth canal (Chlamydia,

Neisseria) person-to-person contact (S. aureus) All babies get silver nitrate and erythromycin in eyes

after birth. If done correctly, this prevents Neisseria infection

(Chlamydia and S. aureus infections are decreased but not prevented).

Disease Chlamydia: conjunctival redness and eyelid edema

with somewhat purulent discharge starting about 1 week after birth. Although Chlamydial conjunctivitis usually responds to topical antibiotics, the infection can be associated with pneumonia, otitis media, and gastrointestinal complications, so systemic antibiotics may be necessary.

Neisseria: acute onset of abundant yellow-green, purulent discharge starting a few days after birth. Rapidly causes severe corneal ulceration, perforation, and blindness. Baby, mom and dad need immediate, systemic antibiotics because of the grave consequences.

Staph aureus: "sticky eye" (crusty, sticky discharge); complications rare.

Post-neonatal conjunctivitisOrganisms Streptococcus pneumoniae Staphylococcus aureus Haemophilus influenzae Chlamydia trachomatis (serotypes A-C or serotypes D-

K, see below) Herpes simplex Adenovirus Transmission direct contact (fingers); eyedroppers; towels; swimming

pools respiratory droplet (S. pneumoniae) sexual transmission (C. trachomatis)Disease symptoms: bilateral redness, pain, itching.


chlamydia conjunctivitis

Neisseria conjunctivitis is hyperpurulent.Treat immediately to prevent blindness.


signs: purulent discharge (if infection is bacterial) or not-very-purulent discharge (if infection is viral)

Many cases resolve in a couple weeks with no sequelae. The big bad exception: Trachoma (Chlamydial

conjunctivitis due to serotypes A through C), which can cause blindness.1 Most Chlamydial conjunctivitis in this country is “inclusion conjunctivitis” (due to serotypes D – K), which is not as serious as trachoma.

1 Chlamydia trachomatis (serotypes A – C) can cause conjunctival scarring → decreased mucin secretion from conjunctival goblet cells → decreased adherence of tears to cornea → corneal ulceration, scarring and blindness. It is a big cause of blindness in developing areas of Asia and Africa; also seen in Native American populations in southwest US.



CorneaKeratitis and corneal ulcerationOrganisms Pseudomonas aeruginosa conjunctivitis-causing bugs (Streptococcus

pneumoniae, Staphylococcus aureus Haemophilus influenzae, Chlamydia trachomatis)

Aspergillus Herpes simplex and zoster Acanthamoeba Transmission usually following trauma also seen in patients using extended-wear soft contacts Acanthamoeba likes home-made contact lens saline Disease Infection of the cornea causes dissolution of the

corneal stroma, and eventually thinning and scarring of the cornea.

Worse, vessels in ciliary body and iris become leaky, and cells and exudate accumulate in anterior chamber ("hypopyon": pus in anterior chamber).1

Pus in the anterior chamber can lead to adhesions between iris and cornea (anterior synechiae) or iris and anterior lens surface (posterior synechiae). Anterior synechiae can lead to increased intraocular pressure and optic nerve damage.

1 Sometimes the inflammatory cells adhere to the cornea, producing "keratic precipitates," the size and shape of which can give clues as to the underlying cause of the inflammation.

intro | orbit | eyelid | conjunctiva | cornea | retina

Don't try to make your own saline solution.

Acanthamoebastellate cyst in corneal

scraping


Retina, choroid and vitreous humorChorioretinitisOrganisms Toxoplasma gondii Cytomegalovirus (CMV) Pneumocystis carinii Mycobacterium avium Candida Onchocerca volvulusTransmission Trans-placental (Toxoplasma, CMV) Hematogenous (Candida can spread to choroid/retina

from IV drug abuse or from candida sepsis due to other causes.)

Vector (Onchocerca, endemic in Central America and tropical Africa, is transmitted through the bite of an infected black fly.)

Disease Symptoms: if unilateral, the patient may squint or

favor the unaffected eye. Photophobia and/or clumsiness (due to decreased vision) can occur.

Untreated, chorioretinitis can lead to partial or total loss of vision.

Onchocerca is different! Microfilariae (tiny worms) develop in subcutaneous nodules, then migrate through skin (causing dermatitis, loss of elasticity) and eye (causing blindness – "river blindness"). Eye lesions begin as keratitis, and extend to anterior chamber, choroid and retina.

EndophthalmitisOrganisms Candida Lots of bacteria, including: Staphylococcus aureus,

Streptococci, and PseudomonasTransmission Endogenous: transmitted through hematogenous

routes (most of these cases are due to fungal infections, particularly Candida)

Exogenous: transmitted by blunt trauma, or by extension of pre-existing keratitis or uveitis (these cases can be caused by many different bacteria, including Staphylococcus aureus, Streptococci, and Pseudomonas).

Disease The term "endophthalmitis" is only applied when

there is pus within the vitreous humor (not just pus in the anterior chamber).


Lots of infectious processes can affect the retina and/or choroid. Usually, infection of one goes along with infection of the other.

Endophthalmitis = infection of the vitreous humor.

Once an infectious process reaches the vitreous humor, it can cause irreversible retinal damage in a matter of hours.


The retina (which lines the vitreous cavity) is very sensitive to pus; after even a few hours of exposure, the retina may be irreversibly damaged.

Endophthalmitis often leads to blindness even when treated aggressively



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