Bacterial

Epidemiology: most common form of keratitis (∼ 90%) [1][2]

Etiology

• Mainly: staphylococci (Staphylococcus aureus), streptococci (Streptococcus pneumoniae), Pseudomonas aeruginosa

• Syphilis

• Enterobacteriaceae (including Klebsiella)

• Risk factors

  • Contact lens use

  • Recent eye surgery or injury

  • Immunodeficiency

  • Lacrimal duct stenosis

Clinical features

• Progressive pain

• Eye redness

• Foreign body sensation

• Purulent discharge

• Photophobia

• Excessive tearing

• Blurry vision

• Conjunctival injection

Subtypes and variants: Pseudomonas keratitis

• Caused by Pseudomonas aeruginosa

• Most common cause of bacterial keratitis in contact lens users [3]

• Fulminant course with severe ulceration

• Corneal destruction/perforation within 2–5 days [4]

Slit lamp examination

• Hypopyon: collection of leukocytes at the bottom of the anterior chamber; occurs in severe cases of keratitis

• Fluorescein staining: round corneal infiltrate or ulcer

  • Creeping ulcer or serpiginous corneal ulcer in pneumococcus infection

  • (Ring‑) ulcer: (ring-shaped) spread of the pathogen in the cornea

  • Thygeson superficial punctate keratitis: point-shaped lesions in the corneal epithelium

Cultures are indicated when the corneal infiltrate is large, central, and extends to the deep stroma, for refractory cases, or those with atypical features. [2]

Topical broad-spectrum antibiotics [2]

• Cefazolin with tobramycin/gentamicin or

• Ofloxacin or

• Ciprofloxacin

Consider corticosteroids following identification of pathogen and ∼2 days of antibiotic therapy

Therapeutic mydriasis may be considered

Corneal transplantation in threatened or existing large perforations, small corneal perforations with consistent bacterial growth, or suppuration despite antibiotics [4]

Prevention: Education on contact lens hygiene

Complications

• Irreversible vision loss

• Corneal destruction (potentially leading up to perforation)

• Leukoma: a dense, white opacity of the cornea caused by scarring

  • Caused by inflammation, injuries, or congenital corneal conditions.

  • Adherent leukoma: part of the iris is attached to the cornea

• Vascularization into the cornea

• ↑ Intraocular pressure; if necessary, reduce intraocular pressure during the acute phase

• Endophthalmitis