keratitis

Question 1

what are the bacterial causes of keratitis?

Answer 1

Staph aureus, Strep pyogenes, Strep pneumoniae, Pseudomonas (Pseudomonas is most common cause of contact lens related corneal ulcers)

Question 2

what are the viral causes of keratitis?

Answer 2

HSV-1, herpes zoster (varicella VZV)

Question 3

what are the fungal causes of keratitis?

Answer 3

andida (yeast), fusarium (filamentous), microsporidia

Question 4

what are the protozoal causes of keratitis?

Answer 4

Acanthamoeba

Question 5

what are the symptoms of keratitis?

Answer 5

• Pain/discomfort
• Red eye
• Blurring of vision (BOV)
• Discharge (watery or mucopurulent)
• Photophobia

Question 6

what are the risk factors for developing bacterial keratitis?

Answer 6

• Trauma, recent ocular surgery involving cornea (e.g. laser refractive surgery, LASIK, corneal transplant surgery)
• Pre-existing chronic corneal disease e.g. Neurotrophic keratopathy, exposure keratopathy
• Contact lens wear (biggest risk factor)

Question 7

what are the risk factors for developing fungal keratitis?

Answer 7

• Trauma: particularly with organic matter
• Contact lens wear
• Immunocompromised host
• Previous topical steroid use

Question 8

what are the signs in epithelial herpes simplex keratitis?

Answer 8

• **Dendritic ulcer (caused by viral replication): linear, branching ulcer, each branch terminating w bulb
• coalesces, i.e. larger epithelial defect, usually in immunosuppressed pts
• metaherpetic if follows dendritic/geographic ulcer that failed to heal
• **Hallmark: Reduced corneal sensation (tested with a cotton swab): HSV uses cellular enzymes of ganglion cells for replication; and the ganglion cells die when HSV is released 🡪 loss of ganglion cells from recurrent infections lead to decreased corneal sensation
• Vesicular rash near the orbit

Question 9

what is the treatment for herpes simplex keratitis?

Answer 9

• topical 3% acyclovir ointment 5x/day for 10-14 days, avoid topical steroids (increases viral replication)
• Skin involvement is treated with 5% acyclovir (higher concentration)

Question 10

what are the investigations for bacterial keratitis?

Answer 10

Corneal scrapings for gram stain & culture (blood, chocolate, Saboraud)

Question 11

what are the signs of bacterial keratitis?

Answer 11

• Conjunctival injection
• Corneal ulcer w/ surrounding corneal oedema
• In severe cases -> anterior uveitis + hypopyon (accumulation of WBC in the anterior chamber 2’ intense inflammation)

Question 12

what is the management for bacterial keratitis?

Answer 12

• Empirical broad spectrum fortified intensive topical abx (cefazolin & gentamicin), subsequently modified based on culture & sensitivity results
• Systemic antibiotics if scleral involvement, severe corneal thinning w/ threatened corneal perforation, and potential for systemic involvement (Neisseria meningitidis /gonorrhoeae, Haemophilus influenzae)
• Manage predisposing factors (e.g. strictly no contact lens wear)

Question 13

what are the signs of fungal keratitis?

Answer 13

• Infiltrate with irregular feathery margins

- Multifocal, satellite lesions

Question 14

what are the complications of keratitis?

Answer 14

• , residual corneal scarring, irregular astigmatism, loss of vision, corneal perforation, and endophthalmitis
• Posterior synechiae (iris adhering to lens due to infection in anterior chamber)
• Secondary acute closure glaucoma if posterior synechiae causes a pupil block
• Cycloplegic spasm (spasm of ciliary muscle of eye)