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Infective keratitis

Specialties > Ophthalmology

Background knowledge 🧠

Definition

  • Infective keratitis is the inflammation of the cornea caused by an infectious agent.
  • May result in corneal ulceration, scarring, and vision loss if untreated.

Epidemiology

  • Common cause of ocular morbidity globally.
  • Higher incidence in tropical and developing countries.
  • Associated with contact lens use, trauma, and immunocompromised states.

Aetiology and Pathophysiology

  • Caused by bacteria (most common), fungi, viruses, or protozoa.
  • Bacterial causes include Staphylococcus aureus, Pseudomonas aeruginosa.
  • Fungal causes often related to trauma with vegetative matter.
  • Viral causes include herpes simplex virus (HSV) and varicella-zoster virus (VZV).
  • Protozoal infections, such as Acanthamoeba, are associated with contact lens use.
  • Infection leads to corneal epithelial defect, stromal infiltration, and possibly perforation.

Types

  • Bacterial keratitis: Rapid progression, purulent discharge.
  • Viral keratitis: HSV or VZV, often recurrent, dendritic ulcers.
  • Fungal keratitis: Insidious onset, feathery edges.
  • Protozoal keratitis: Associated with contact lens use, severe pain.

Clinical Features 🌡️

Symptoms

  • Eye pain, often severe.
  • Redness and photophobia.
  • Blurred vision and tearing.
  • Foreign body sensation.
  • Discharge, which may be purulent (bacterial) or watery (viral).

Signs

  • Conjunctival injection, particularly around the limbus (ciliary flush).
  • Corneal ulcer or infiltrate visible on slit lamp exam.
  • Hypopyon in severe cases.
  • Decreased corneal sensation (especially in viral keratitis).
  • Stromal edema and corneal opacification.

Investigations 🧪

Tests

  • Slit lamp examination with fluorescein staining.
  • Corneal scraping for microbiological culture and sensitivity.
  • Polymerase chain reaction (PCR) for viral or protozoal causes.
  • Confocal microscopy for Acanthamoeba.
  • Chest X-ray or Mantoux test if tuberculosis suspected.

Management 🥼

Management

  • Prompt initiation of broad-spectrum topical antibiotics for bacterial keratitis.
  • Antiviral agents for HSV keratitis (e.g., topical acyclovir).
  • Antifungal drops for fungal keratitis (e.g., natamycin or amphotericin B).
  • Cycloplegics for pain relief and to prevent synechiae.
  • Avoid corticosteroids unless under specialist advice (risk of worsening infection).
  • Surgical intervention (e.g., corneal transplantation) in severe or unresponsive cases.

Complications

  • Corneal scarring leading to visual impairment.
  • Corneal perforation and subsequent endophthalmitis.
  • Glaucoma secondary to inflammation.
  • Cataract formation due to chronic inflammation or steroid use.
  • Loss of the eye in severe, untreated cases.

Prognosis

  • Depends on the causative agent and promptness of treatment.
  • Bacterial keratitis: Good prognosis with early, appropriate therapy.
  • Fungal and Acanthamoeba keratitis: More challenging to treat, higher risk of complications.
  • Viral keratitis: Prone to recurrence, long-term antiviral prophylaxis may be needed.
  • Overall, risk of significant vision loss if diagnosis or treatment is delayed.

Key Points

  • Infective keratitis is an ocular emergency requiring prompt recognition and treatment.
  • Contact lens users are at high risk, and proper lens hygiene is crucial.
  • Early referral to an ophthalmologist is essential for suspected cases.
  • Empirical broad-spectrum antibiotics should be started immediately if bacterial keratitis is suspected.
  • Avoid corticosteroids in the acute phase unless advised by a specialist.

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Ophthalmology