2-19 - MicrobialKeratitis

Question 1

General signs of corneal inflammation?

Answer 1

• 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)

Question 2

Explain why CLs increase chances of corneal infection

Answer 2

• 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.

Question 3

General signs of infectious keratitis
- How to identify if lesion more likely from infection?

Answer 3

• Red eye (injection)
• Epithelial defect
• Corneal opacification
• Hypopyon

PEDAL
- Pain
- Epithelial defect
- Discharge
- AC reaction (cells/flare)
- Location (central generally)

Question 4

Bacterial Keratitis
- General information
- Risk factors

Answer 4

• 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.

Question 5

Bacterial Keratitis
- Signs + Symptoms

Answer 5

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

Question 6

Bacterial Keratitis
- Pathophysiology

Answer 6

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

Question 7

Epithelial Herpes Simplex Keratitis
- Signs + symptoms

Answer 7

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)

Question 8

Stromal Herpes Simplex Keratitis
- Signs + symptoms

Answer 8

• 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.

Question 9

Endothelial Herpes Simplex Keratitis
- Signs + symptoms

Answer 9

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

Question 10

Herpes Zoster Ophthalmicus
- General herpes zoster information

Answer 10

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.

Question 11

Herpes Zoster Ophthalmicus
- Disease course
- Signs + symptoms

Answer 11

• 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

Question 12

Protozoan infection in the eye
- General information
- Risk factors

Answer 12

Acanthamoeba keratitis
- Either trophozoite (active) or cyst (dormant)
Risk factors:
- Epithelial defect
- Soft CLs
- Spa pools
Often misdiagnosed early on so harder to treat.

Question 13

Protozoan infection in the eye
- Signs + symptoms

Answer 13

Symptoms:
- Lots of pain
- Photophobia
- Blurred vision
Signs:
- Conjunctival injection
- Epithelial/sub-epithelial infiltrates
- Ring-like infiltrate
- If infiltrates enlarge, form abscess -> perforation

Question 14

Fungal Keratitis
- General information
- Risk factors

Answer 14

Yeast e.g. Candida or Aspergillus
Risk factors:
- Ocular trauma (especially if organic matter)
- Topical steroid therapy
- Pre-existing ocular or systemic immunosuppressive disease.

Question 15

Fungal Keratitis
- Signs + symptoms

Answer 15

Symptoms:
- Pain
- Photophobia
- Delayed presentation post-red eye
Signs:
- Corneal infiltrate dense w/ feathery (indistinct) border
- Corneal oedema
- AC reaction w/ hypopyon