2-19 - MicrobialKeratitis Flashcards
General signs of corneal inflammation?
- Epithelial cell loss (e.g. SPK)
- Infiltration of immunological cells (seen as stromal infiltrates which are fuzzy gray)
- Corneal swelling (oedema)
- BV ingrowth = corneal pannus (neovasc)
Explain why CLs increase chances of corneal infection
- Pathogens survive between CLs and cornea w/o being washed by tears
- CL wear causes micro-trauma
- Pathogens spend longer in contact to epithelium so more likely to traverse it/break it. Will induce immune response.
General signs of infectious keratitis
- How to identify if lesion more likely from infection?
- Red eye (injection)
- Epithelial defect
- Corneal opacification
- Hypopyon
PEDAL
- Pain
- Epithelial defect
- Discharge
- AC reaction (cells/flare)
- Location (central generally)
Bacterial Keratitis
- General information
- Risk factors
- Acute, sight-threatening
Only few can penetrate intact epithelium, most associated w/ compromised epithelial integrity e.g.
– CLs (w/ extended wear especially) increases contact time
– Trauma
– Tear film deficiency (dry eye) etc.
Bacterial Keratitis
- Signs + Symptoms
Symptoms:
- FB sensation
- Photophobia
- Pain more
Signs:
- Conjunctival injection (red)
- Epithelial defect w/ infiltrate
- Mucopurulent Discharge
- Secondary sterile AC reaction (w/ or w/o hypopyon)
- Location either central or peripheral
Bacterial Keratitis
- Pathophysiology
Pathophysiology:
- Colonises stroma, releases enzymes + toxins (antigens)
- Antigens cause immune response
- Polymorphonuclear leukocytes (PMNs) aggregate (infiltrate)
- PMNs phagocytose bacteria
- Scarring of stroma
- Non-CL wear = Staphylococcus Aureus
- CL-wear = Pseudomonas Aeruginosa
Epithelial Herpes Simplex Keratitis
- Signs + symptoms
Symptoms:
- Unilateral, w/ or w/o history
- Mild discomfort, w/ or w/o reduced VA
Signs:
- Conjunctival injection
- Watery discharge
- Branching dendritic ulcer w/ characteristic terminal bulbs. Can coalesce to become geographic ulcer (see slide)
Stromal Herpes Simplex Keratitis
- Signs + symptoms
- Rarer than epithelial
- Active viral invasion + tissue necrosis
Signs: - Conjunctival injection
- “Cheesy” necrotic stroma w/ or w/o epithelial defect
- Ant. Uveitis w/ KPs under affected area
- w/ or w/o vascularised scar
Note: Keratic Precipitates are… - Common in anterior inflammation
Punctate KPs: - Inflammatory cellular deposites on endothelium. Made of macrophages and epithelioid cells
- Newer KPs more white + round, older KPs more irregular, faded, and pigmented.
Endothelial Herpes Simplex Keratitis
- Signs + symptoms
Disciform HSK
- Graudal onset, painless, blurred vision
Signs:
- Reduced corneal sensation
- Epithelial and stromal oedema
- KPs under lesion
- AC reaction
- Descemet’s membrane folding
- Higher IOP
Herpes Zoster Ophthalmicus
- General herpes zoster information
Varizella virus (chicken pox)
- Dormant in dorsal root ganglia
- Reactivates into herpes zoster (shingles)
- Painful skin rash distributed by trigeminal nerve.
If affect ophthalmic division of trigeminal nerve, HZO.
- Hutchingson’s sign if rash reaches tip of nose (when nasocilliary nerve is affected)
- More likely with age.
Herpes Zoster Ophthalmicus
- Disease course
- Signs + symptoms
- Prodromal = 1 week of fever, heacdache, malaise
- Midline rashes
- 50% get eptihelial keratitis – Small fine pseudo dendritic ulcers w/ tapered ends (no end bulbs). 1 week resolution
- 5% get nummular keratits (subepithelial, stromal) -> disciform keratitis
Long term: - Nerve damage
- Scarring
- Chronic inflammation
- Dry eye
- Post-herpectic pain
Protozoan infection in the eye
- General information
- Risk factors
Acanthamoeba keratitis
- Either trophozoite (active) or cyst (dormant)
Risk factors:
- Epithelial defect
- Soft CLs
- Spa pools
Often misdiagnosed early on so harder to treat.
Protozoan infection in the eye
- Signs + symptoms
Symptoms:
- Lots of pain
- Photophobia
- Blurred vision
Signs:
- Conjunctival injection
- Epithelial/sub-epithelial infiltrates
- Ring-like infiltrate
- If infiltrates enlarge, form abscess -> perforation
Fungal Keratitis
- General information
- Risk factors
Yeast e.g. Candida or Aspergillus
Risk factors:
- Ocular trauma (especially if organic matter)
- Topical steroid therapy
- Pre-existing ocular or systemic immunosuppressive disease.
Fungal Keratitis
- Signs + symptoms
Symptoms:
- Pain
- Photophobia
- Delayed presentation post-red eye
Signs:
- Corneal infiltrate dense w/ feathery (indistinct) border
- Corneal oedema
- AC reaction w/ hypopyon
