About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Sight-threatening — corneal infection leads to ulceration and scarring
- Contact lens wear is the biggest risk factor in the UK
- HSV keratitis = dendritic ulcer on fluorescein — ganciclovir ointment (NOT steroids alone)
- Bacterial keratitis: intensive topical fluoroquinolone hourly — same-day ophthalmology
- Acanthamoeba: severe pain OUT OF PROPORTION + ring infiltrate + water exposure with lenses
Overview
Keratitis is corneal inflammation. Microbial keratitis can be bacterial (Pseudomonas in contact lens wearers, Staphylococcus in non-lens wearers), viral (HSV is the commonest infectious cause of corneal blindness in developed countries), fungal (trauma with organic material), or parasitic (Acanthamoeba — contact lens use and water exposure).
Epidemiology
Incidence approximately 5–10 per 100,000 per year in the UK. Contact lens wear accounts for ~50% of cases. Acanthamoeba keratitis is rare (~100 cases/year in UK) but devastating.
Clinical Features
Symptoms
Severe eye pain
Photophobia and reduced visual acuity
History of contact lens wear (especially overnight or in water)
Signs
White corneal infiltrate or opacity
Positive fluorescein staining
Dendritic ulcer = HSV keratitis (pathognomonic)
Hypopyon in severe bacterial keratitis
Ring infiltrate = Acanthamoeba keratitis
Investigations
First-line
Slit-lamp with fluoresceinEssential — demonstrates ulcer and infiltrate
Second-line
Corneal scrape for MC&SGram stain, bacterial/fungal/Acanthamoeba culture
Corneal PCRFor HSV, VZV, Acanthamoeba
Specialist
Confocal microscopyIdentifies Acanthamoeba cysts and fungal elements in vivo
1
General
- STOP contact lens wear
- Same-day urgent ophthalmology referral
2
Bacterial keratitis
- Ofloxacin 0.3% or moxifloxacin 0.5% hourly day and night
- Cycloplegic for pain relief
- Do NOT patch the eye
3
HSV keratitis
- Ganciclovir 0.15% gel 5 times daily
- Do NOT give steroids alone — worsens epithelial disease
- Oral aciclovir 400 mg BD for recurrence prophylaxis
4
Acanthamoeba keratitis
- PHMB 0.02% + propamidine (Brolene) 0.1% hourly initially
- Treatment for months — cyst resistance
Complications
- Corneal scarring: May need keratoplasty
- Corneal perforation
- Endophthalmitis
- Recurrent HSV keratitis: ~50% recurrence
UKMLA Exam Tips
- 1Contact lens + painful red eye = keratitis until proven otherwise — STOP lenses, REFER
- 2Dendritic ulcer on fluorescein = HSV — ganciclovir, NEVER steroids alone
- 3Pseudomonas = classic contact lens keratitis organism
- 4Fluorescein staining is the single most important bedside test for any painful red eye
practicetest your knowledge on Corneal Ulcer and KeratitisApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — Ophthalmology and beyond.
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