Cornea
Microbial Keratitis
Also known as: corneal ulcer, bacterial keratitis, corneal infection, contact lens keratitis, corneal infiltrate, infectious keratitis, pseudomonas keratitis, acanthamoeba keratitis
Filed as: Emergency
Source-cited from the record's own evidence list. Clinical content programme led by Dr Ankit Mathur, PhD, Grad Cert Ocu Thera, B.S. Optom. How the clinical content is governed
Clinical decision support only
Overview
Infection of the corneal stroma — a sight-threatening ophthalmic emergency. Contact lens wear is the leading risk factor in developed countries. Presents with pain, photophobia, diffuse injection, anterior chamber reaction, and a visible white corneal infiltrate or ulceration over infiltrate. Requires immediate ophthalmology referral. Do NOT instil topical steroids.
Recognition
Symptoms: what patients report
- Acute severe pain — often out of proportion to apparent redness.
- Photophobia.
- Reduced visual acuity — may be significant.
- Purulent or mucopurulent discharge.
- Marked tearing.
- History of contact lens wear, especially overnight or extended wear, swimming, showering, hot tub, or tap-water exposure in lenses, poor case hygiene, topping off solution, delayed case replacement, cosmetic lenses, or overwear beyond replacement schedule.
- Recent ocular surgery, corneal trauma, blepharitis, prior herpetic disease, or dry eye.
Signs: what the examination shows
- White or grey stromal infiltrate / white corneal lesion — the defining sign.
- Epithelial defect overlying the infiltrate, staining with fluorescein.
- Ulceration over infiltrate strongly supports infectious corneal ulcer rather than a sterile infiltrate.
- Central or paracentral involvement, proximity to the visual axis, deeper stromal involvement, thinning, or perforation concern increases urgency.
- Surrounding corneal oedema and haze.
- Diffuse or circumcorneal injection.
- Anterior chamber reaction — cells or flare may accompany more significant infection.
- Hypopyon (cells layering in the inferior anterior chamber) — indicates severe infection.
- Lid oedema and discharge.
- Ring infiltrate pattern or pain disproportionate to visible signs raises concern for Acanthamoeba keratitis.
What OptoGuide™ covers for microbial keratitis
- Pattern reasoning: what this combination of findings points to, and its differentiators
- Don't-miss risks and escalation triggers
- Management tiers with linked Australian therapeutics
- Referral urgency, specialty, and letter drafting
Sources
- Microbial keratitis (bacterial, fungal) — College of Optometrists CMG
- Bacterial Keratitis — EyeWiki
- Anterior Eye Disease and Therapeutics A-Z (Bruce & Loughnan) — standard reference text
- Endophthalmitis in Advanced Microbial Keratitis: Risk Factors and Examination Findings. Christopher KL, Hood CT, Mian SI, Ayres B. Cornea. 2020;39(9):1096-1101.
- Eye Infections. Durand ML, Barshak MB, Sobrin L. The New England Journal of Medicine. 2023;389(25):2363-2375.
- Infectious Keratitis in 2021. Durand ML, Barshak MB, Chodosh J. JAMA. 2021;326(13):1319-1320.
Standard texts: Kanski's Clinical Ophthalmology: A Systematic Approach, The Wills Eye Manual, Oxford Handbook of Ophthalmology, Oxford American Handbook of Ophthalmology, Signs in Ophthalmology: Causes & Differential Diagnosis.