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What is Corneal Infection (keratitis)?

The cornea is the ‘central clear window of the eye;’ a transparent outer layer covering the front part of the eye. It helps shield the rest of the eye from germs, dust and other harmful matter. The cornea shares this protective task with the eyelid, eye socket, tears and the sclera. Together with the tear film, it is the major structure to focus light and vision, accounting for approximately two-thirds of the eyes’ focusing power. As such, any small alterations to the cornea can dramatically affect vision.

What Causes Corneal Infection (keratitis)

Corneal infections can be caused by

  • Bacteria – numerous causes but risk factors include contact lens wear, injuries and use of topical steroid medication at the time of onset. Treatment includes very frequent (ie. every hour) medications to sterilise the eye surface. Sometimes, multiple antibiotics are required to ensure the organism is being adequately treated. Anti-scarring (topical steroid) medications may cautiously be used to limit scarring that can result from deep inflammation and infections as well as adjacent inflammation that may result.
  • Viruses – the two most common are:
    • Herpes Simplex Keratitis – aka the cold sore virus, this can cause cornea scarring and inflammation that can be recurrent in nature. Treatment involves antiviral and anti-scarring medication and typically takes weeks to months to resolve. Preventative treatment may be needed to prevent recurrence as it cannot be cured or eliminated.
    • Herpes Zoster virus – aka shingles, caused the by chickenpox virus, can cause corneal scarring and inflammation. It is usually precipitated by scars on the head and scalp on the same side. It usually flairs up in patients with impaired immune systems. Treatment includes antiviral and anti-inflammatory medications. A detailed ocular exam is required to exclude other eye complications or involvement. It may be recurrent as it cannot be cured or eliminated.
  •  Fungal keratitis
    • Whilst uncommon, this can be a particularly difficult infection to treat. Risk factors include eye injury, topical steroid use and contact lens wear. It is usually diagnosed by sending a sample to pathology to confirm, and is treated with antifungal medications.
  • Parasites – ie Acanthomoeba keratitis
    • This is rare, but is is usually seen in patients who wear contact lenses. Acanthomoeba is a water based organism, which can cause keratitis and is both difficult to diagnose and treat. Diagnosis may involve testing of contact lenses, eye surface cells specimens or special microscopic examination. Treatment involves multiple eye drops that work in different ways, as it is resistant to many treatments.

Autoimmune causes of corneal inflammation or keratitis are possible, and may be related to immune disorders in the rest of the body, for example rheumatoid arthritis.

Symptoms of Corneal Infection (keratitis)
  • Pain
  • Sensitivity to light
  • Reduced or blurred vision
  • Ocular discharge
  • White spot in the eye or cornea
  • Floaters
Treatment of Corneal Infection (keratitis)

Treatment is individualized in all cases so it is difficult to generalize.

  • Treating the underlying infection – if present or excluding one if suspected. This can include eye swabs and samples sent to patholoty and treatment for suspected causes commences immediately whilst awaiting results
  • Preventing complications – scarring of the cornea can cause irreversible vision loss so treatment with anti-scarring medications (aka topical steroids) may be needed once the infection is adequately controlled
  • Lubrications – a moist eye is faster to heal, so lubricants are often used for comfort and to assist healing

After the infection or acute ulcer is treated, restorative laser or surgery may be needed to obtain the best vision possible. 

Important Notes
  • Corneal infections may cause rapid vision loss
  • Symptoms include pain, blurred vision and discharge
  • Contact lens wear is a major risk factor for all corneal infections, and the contact lens may be sent as a sample to investigate the cause so should be kept if suspected
  • Treatment includes antibiotics to the likely organisms and tests sent to investigate for all causes, along with anti-inflammatory and lubricating medications
  • Restorative and rehabilitative treatment may be needed after the eye has settled