What is the treatment for a corneal infection?

Treatment of Corneal Infection

For bacterial keratitis, the most effective treatment is topical fluoroquinolones such as moxifloxacin 0.5% applied frequently, starting with loading doses every 5-15 minutes followed by hourly application for severe cases. 1

Initial Assessment and Diagnosis

• Corneal infections should be examined by an ophthalmologist as part of the initial assessment to determine the severity and type of infection 1
• Fluorescein staining should be performed to identify epithelial defects and assess the extent of corneal involvement 1
• Smears and cultures are specifically indicated when:
  • The corneal infiltrate is central, large (>2 mm), or has significant stromal involvement/melting
  • The infection is chronic or unresponsive to broad-spectrum antibiotics
  • There is a history of corneal surgeries
  • Atypical features suggest fungal, amoebic, or mycobacterial keratitis
  • Multiple infiltrates are present on the cornea 1

Treatment Algorithm for Bacterial Keratitis

Mild to Moderate Bacterial Keratitis

• Begin with topical fluoroquinolones (e.g., moxifloxacin 0.5%) applied 1 drop every hour while awake for the first 24-48 hours 1, 2
• After 48 hours of improvement, reduce frequency to every 2 hours while awake 3
• Continue treatment for 7-10 days, not tapering below 3-4 times daily to avoid developing resistance 3
• Add a cycloplegic agent if substantial anterior chamber inflammation is present 1

Severe Bacterial Keratitis

• Begin with loading doses of topical antibiotics every 5-15 minutes followed by hourly application 1, 4
• For central or large infiltrates, consider combination therapy with fortified antibiotics 1
• Daily ophthalmological review is necessary during the acute illness 1
• Ocular hygiene to remove inflammatory debris should be performed daily 1

Contact Lens-Related Keratitis

• Immediately discontinue contact lens wear 4
• Higher risk of Pseudomonas infection requires aggressive antibiotic therapy 4
• Avoid bandage contact lens use in these cases 5

Monitoring Treatment Response

Positive signs of response to therapy include:

• Reduced pain and discharge 3
• Decreased eyelid edema and conjunctival injection 3
• Consolidation and sharper demarcation of stromal infiltrate perimeter 3
• Decreased density of stromal infiltrate and reduced stromal edema 3
• Initial re-epithelialization and cessation of progressive corneal thinning 3

Special Considerations

Corticosteroid Use

• Corticosteroids may be considered after 24-48 hours when the causative organism is identified and/or infection is responding to therapy 1
• Topical corticosteroids should be avoided in cases of suspected Acanthamoeba, Nocardia, or fungal infections 1
• Topical corticosteroids can mask signs of corneal infection 1

Fungal Keratitis

• Requires different treatment approach with antifungal agents such as natamycin 5% for filamentous fungi 6
• Topical amphotericin B (0.1-0.3%) is often the treatment of choice for Candida infections 6
• Avoid corticosteroids in suspected fungal infections 1, 6

Complicated Cases

• For persistent epithelial defects where infection is controlled, consider adjunctive therapies such as lubrication, bandage contact lens, or amniotic membrane coverage 1
• Application of amniotic membrane may decrease inflammation and stabilize the ocular surface 1
• For cases with corneal thinning or impending perforation, consider tissue adhesive, penetrating keratoplasty, or lamellar keratoplasty 1

Common Pitfalls and Caveats

• Avoid patching the eye in contact lens wearers with corneal abrasions due to increased risk of bacterial keratitis 1, 5
• Most antibiotic eye drops should not be tapered below 3-4 times daily as low doses are subtherapeutic and may increase antibiotic resistance 3
• Modification of therapy should be considered if the eye shows no improvement within 48 hours 3
• Be aware of increasing resistance of MRSA and Pseudomonas aeruginosa to topical fluoroquinolones 1
• Prolonged use of topical antibiotics can cause toxicity, so taper as infection improves 3

Emerging Treatments

• Corneal cross-linking has shown promise as an adjunctive treatment for bacterial keratitis, especially for more shallow infiltrates 1
• Topical povidone-iodine 1.25% has been shown to be as effective as topical antibiotics in some studies and may be a cost-effective alternative in developing countries 1