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Eyes & Vision

Infective Keratitis

Infective keratitis is a sight-threatening corneal infection causing a painful red photophobic eye with an infiltrate or ulcer; contact-lens-associated disease and Acanthamoeba require emergency ophthalmology, microbiological assessment and specialist antimicrobial treatment.

In a nutshell

Infective keratitis is a sight-threatening corneal infection: painful red photophobic eye, blurred vision and a white/grey corneal infiltrate or ulcer, often in a contact-lens wearer. Arrange urgent ophthalmology, stop lenses and retain lenses/case. Significant ulcers need corneal scrape and intensive specialist topical antimicrobials. Pain out of proportion suggests Acanthamoeba; a dendritic ulcer suggests HSV and must not receive steroid monotherapy; fungal disease needs specialist antifungal treatment.

Classic presentation

A contact-lens wearer develops a painful red watering eye with photophobia and blurred vision; slit lamp shows a white corneal infiltrate with an overlying fluorescein-staining epithelial defect.

Key points

  • Keratitis can scar, melt and perforate the cornea, so it is an ophthalmic emergency.
  • Contact-lens wear, especially overnight wear, poor hygiene or water exposure, is a major risk factor.
  • A corneal infiltrate/ulcer with pain or reduced vision needs urgent eye-care assessment; significant ulcers need scrape/culture and intensive treatment.
  • Severe pain out of proportion suggests Acanthamoeba; stop lenses, retain lens/case and refer same day for specialist therapy.
  • A dendritic epithelial ulcer suggests HSV: use antiviral treatment and never steroid monotherapy.
  • Steroids, cycloplegia and treatment of thinning/perforation are ophthalmology-led and only used for defined indications.

First-line investigation

Urgent slit-lamp and fluorescein assessment of acuity, infiltrate/ulcer, chamber, hypopyon and thinning; corneal scrape/culture for significant, central, deep, atypical or progressive ulcers.

Management

Stop lenses and arrange emergency eye review

  • Painful red eye with corneal infiltrate/ulcer, especially with contact-lens use, needs urgent ophthalmology; stop lenses immediately and retain the lens, case and solution.1,2,6

Assess severity and obtain microbiology

  • Use slit lamp/fluorescein to assess acuity, infiltrate and ulcer depth, chamber reaction, hypopyon and thinning; scrape significant, central, deep, atypical or progressive ulcers before/as treatment begins where feasible.1,2

Start intensive specialist antimicrobial treatment

  • The ophthalmology team should start frequent topical antibiotic therapy, often a fluoroquinolone or fortified regimen under local/BNF/microbiology guidance; serious disease may need day-and-night treatment, admission and close review.1,7,8

Use organism-specific treatment and cautious steroids

  • Treat HSV with antiviral therapy, Acanthamoeba with prolonged specialist anti-amoebic drops and fungal disease with specialist antifungals; only add topical steroid after infection control and ophthalmology review, never as HSV monotherapy.2,1,5,4

Monitor healing and prevent recurrence

  • Monitor acuity, ulcer/infiltrate, thinning, chamber reaction and pressure; escalate worsening pain/vision, hypopyon, thinning or leak. Restart lenses only after eye-team clearance and reinforce no tap water, no sleeping/swimming in lenses and safe case hygiene.1,2,3,6

Exam traps

  • A painful red eye with corneal infiltrate in a contact-lens wearer is not simple conjunctivitis.
  • Do not delay same-day referral for routine community antibiotic drops when the ulcer is central, large, deep, progressive or vision-threatening.
  • Pain out of proportion to early signs is a clue to Acanthamoeba, not reassurance that the cornea looks mild.
  • A dendritic HSV ulcer must not be treated with topical steroid alone.
  • Do not restart contact lenses until the eye service confirms healing and gives lens-safety advice.

Illustrations

Hypopyon in severe infective keratitisSlit-lamp photograph showing corneal opacity with a layered hypopyon, illustrating severe anterior-chamber inflammation. Label it as an emergency clinical example rather than a diagnostic substitute.Imrankabirhossain, Wikimedia Commons · CC-BY-SA-4.0
Herpes simplex dendritic ulcerFluorescein-stained branching dendritic epithelial ulcer of HSV keratitis under blue light; include the warning that steroid monotherapy can worsen active infection.Imrankabirhossain, Wikimedia Commons · CC-BY-SA-4.0

Key sources

  1. College of Optometrists, Clinical Management Guideline: Microbial keratitis (bacterial, fungal) (CMG Microbial keratitis (bacterial, fungal), version 14)Updated 15 Oct 2024
  2. College of Optometrists, Clinical Management Guideline: Microbial keratitis (Acanthamoeba sp.) (CMG Acanthamoeba keratitis, version 15)Updated 15 Apr 2026
  3. College of Optometrists, Contact lenses for overnight wear (Guidance A442–A444)
  4. Moorfields Eye Hospital, Herpes simplex virus keratitis (Moorfields patient information hub)
  5. NHS, Herpes simplex eye infections (NHS Health A to Z: herpes simplex eye infections)Updated 25 Apr 2023
  6. Moorfields Eye Hospital, Acanthamoeba keratitis (Moorfields patient guidance)
  7. NHS Lanarkshire Joint Adult Formulary, Ophthalmic infections (Anti-infective eye preparations, reviewed 2022)Updated 31 Jan 2022
  8. BNF, Ciprofloxacin (BNF drug monograph: ciprofloxacin)
  9. BNF, Aciclovir (BNF drug monograph: aciclovir)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.