Keratitis

Keratitis is inflammation of the cornea, a clear and transparent covering over the iris and pupil. Important forms of keratitis include bacterial, herpes zoster, herpes simplex, and Acanthamoeba keratitis. Most corneal injuries and infections are associated with severe pain, although sometimes pain is absent. Other findings include irritation, eye redness, watery or purulent secretion, and impaired vision. Diagnosis is usually based on clinical findings and slit-lamp examination. Keratitis is an emergent disorder that can lead to irreversible vision loss left untreated.

• Epidemiology: most common form of keratitis (∼ 90%)
• 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
  • Foreign body sensation
  • Purulent discharge
  • Photophobia
  • Excessive tearing
  • Blurry vision
  • Eye redness
  • Conjunctival injection
  • Special form: Pseudomonas keratitis
    • Caused by: Pseudomonas aeruginosa
    • Most common cause of bacterial keratitis in contact lens users
    • Characterized by a fulminant course with severe ulceration and corneal destruction/perforation within 2–5 days
• Diagnostics
  • 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
  • Cultures are indicated when the corneal infiltrate is large, central, and extends to the deep stroma, for refractory cases, or those with atypical features.
• Treatment
  • Topical broad-spectrum antibiotics
    • 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
• 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.
  • Vascularization into the cornea
  • ↑ Intraocular pressure; if necessary, reduce intraocular pressure during the acute phase
  • Endophthalmitis

Bacterial keratitis should be treated as an ophthalmic emergency because of the risk of irreversible vision loss!

References:^{[1][2][3][4][5][6]}

Herpes simplex keratitis

• Etiology: infection due to reactivated herpes simplex virus (HSV) type 1 from the trigeminal ganglion
• Clinical features
  • Similar to viral conjunctivitis, but usually unilateral
  • Eye redness
  • ± Eye pain
  • Foreign body sensation
  • Photophobia
  • Blurry vision; can lead to vision loss if untreated
• Diagnostics
  • Fluorescein staining: superficial corneal erosions (dendritic ulcers) that resemble the branches of a tree (geographic ulcers may be seen when dendritic ulcers widen in shape)
  • Direct fluorescein antibody test (HSV antigen detection) or polymerase chain reaction (PCR) test
• Treatment for epithelial HSV keratitis
  • Topical trifluridine or ganciclovir
  • Oral antiviral (e.g., acyclovir) when topical treatment cannot be administered by the patient, prophylactic treatment after surgery, or refractory cases despite topical treatment
  • Corneal transplantation for patients with severe corneal scarring

Glucocorticoids should not be used in initial treatment of dendritic epithelial keratitis!

Herpes zoster keratitis

• Etiology: reactivated herpes zoster virus (involvement of the ophthalmic nerve ); see also herpes zoster ophthalmicus.
• Clinical features
  • Prodrome: headache, malaise, fever
  • Impaired vision
  • Eye irritation (foreign body sensation)
  • Photophobia
  • Eye pain
  • In the innervation area of the ophthalmic nerve (forehead, bridge, and tip of the nose):
    • Vesicular eruption
    • Anesthesia dolorosa
• Diagnosis
  • Slit-lamp examination and fluorescein staining
    • 1–2 days: punctate lesions on the corneal surface
    • 4–6 days: dendritic lesions on the corneal surface
• Treatment: oral acyclovir, valacyclovir, or famciclovir
• See also herpes zoster ophthalmicus.

Adenovirus

See epidemic keratoconjunctivitis.

References:^{[7][8][9][10][11][12][13][14]}

• Etiology: Acanthamoeba infection
• Characteristics
  • Rare condition
  • Primarily occurs in immunocompetent contact lens wearers
  • Progressive course for several weeks despite an attempt of antibiotic treatment
• Clinical features
  • Severe pain
  • Eye redness
  • Photophobia
  • Epiphora
  • Decrease in vision
  • Corneal ring infiltrate (late-stage)
• Diagnostics
  • Slit-lamp examination and/or fluorescein staining: features of epithelitis and stromal disease
  • Culture and microscopy of eye scraping
  • Pathogen detection is often difficult.
• Treatment
  • Topical antiseptic (e.g., chlorhexidine) with propamidine
  • Corneal transplantation for refractory cases

References:^[15][16]