5.12 Keratitis, Microbial, Bacterial

eyes.nhs.scot/
Eyecare Guidelines/
Section 5 - Cornea/
5.12 Keratitis, Microbial, Bacterial

Date of last review:

10/04/2026

Date of next review:

10/04/2028

Date of publication:

20/04/2026

Differential diagnosis ⁽¹⁾

Fungal Keratitis
Corneal inflammatory non-infectious lesions (contact lens related or marginal keratitis)
Peripheral, small (0.5-1.5 mm) with less anterior chamber response
Macro corneal erosion in vernal keratoconjunctivitis
Acanthamoeba keratitis (AK)
Suspect AK if multiple epithelial or subepithelial infiltrates, perineural infiltrates or dendritiform epithelial lesions)
Herpes Simplex keratitis

Possible management by optometrist

Advice ⁽¹⁾

Cease contact lens wear
Warn contact lens wearers not to discard their lenses or lens cases, but to retain them if needed for culture
Emergency (same day) referral is indicted if any of the following signs are present:
- Infiltrate >1mm
- 2 or more adjacent lesions
- Location 3mm or less from corneal centre
- Anterior chamber reaction (≥10 cells in a 1mm beam (≥ 1+ on the SUN scale))
- Signs suggestive or fungal or acanthamoeba keratitis
- High likelihood of poor patient compliance to treatment

NB. These sight-threatening characteristics are indications for corneal scraping for microbiological Gram stain and culture, which should be performed prior to initiating antimicrobial therapy.

Treatment ⁽¹⁾

For lesions <1 mm without high-risk features:
Fluoroquinolone monotherapy

Typical adult dosage/duration

(Blue text = IP, black text = non-IP)

Ofloxacin 3mg/ml eye drops ^(1,5) (POM generic): One drop ⁽⁷⁾in the affected eye(s) every 2-4 waking hours for the first 2 days then four times daily. Treatment should not exceed 10 days ⁽⁷⁾
Cyclopentolate hydrochloride 1% eye drops ⁽⁷⁾ (POM generic): One drop up to 3 times daily, consider reducing (or stopping) as condition improves ^(6,7) (consult local guidance as they may vary on timescales⁽⁷⁾

NB. Monitor closely during this period and refer same day if not healing or if symptoms worsen ⁽¹⁾

Regimens should be adjusted according to severity and patient factors (e.g. age, weight, pregnancy, renal function). Prescribing should follow local formulary and national guidance where available ⁽⁷⁾.

In cases of known sensitivities, please consult local formularies for alternative options ⁽⁷⁾.

Further management options

Emergency referral (same day) indicated ⁽¹⁾ when:

Fungal keratitis or acanthamoeba keratitis is suspected
Any sight threatening features listed above are present
- Actions:
  - Urgently refer to hospital eye service
  - Instruct patient to bring lenses and cases

Normally no referral required where ⁽¹⁾:

Lesions <1 mm
No sight threatening characteristics
- Actions:
  - Manage empirically with topical antimicrobials
  - Referral where deterioration occurs

Treatment may be provided within available locally enhanced schemes, or by community IP optometrists/OMPs, as appropriate ⁽⁷⁾

Possible management in secondary care or local/community pathways where available

See further management options ^{(1, 7)}
Corneal scraping for culture and antibiotic sensitivity, due to evolving pathogen profiles and resistance⁽¹⁾
PCR testing where available ⁽¹⁾
Possible hospital admission for poor compliance, overnight therapy, or severe lesions (axial, ≥6 mm, or ≥50% stromal thinning) ⁽¹⁾
Cycloplegics for comfort ⁽¹⁾
IOP lowering therapy if required ⁽¹⁾
Topical steroids only once infection is controlled (evidence remains limited) ⁽¹⁾
Corneal crosslinking may be considered in selected cases ⁽¹⁾

College of Optometrists Clinical Management Guideline⁽¹⁾

Microbial keratitis (bacterial, fungal) - College of Optometrists*

*With special thanks to The College of Optometrists for providing the evidence framework for diagnosis and management from the Clinical Management Guidelines (CMGs) for this condition. All references to the College/CMGs are included where appropriate and form the basis of the Community Eyecare Guidelines.

Guidance is informed by the following sources

College of Optometrists Clinical Management Guidelines Clinical Management Guidelines - College of Optometrists
Advisory alignment with the College of Optometrists Formulary Optometrists' Formulary - College of Optometrists
Advisory alignment with the BNF BNF (British National Formulary) | NICE
Advisory alignment with the Summary Product Characteristics taken from the EMC Home - electronic medicines compendium (emc)
Advisory alignment with Scottish Health Board formularies (where a clear majority is present) *
Advisory alignment with expert consensus (CEGG), informed by sources 2-5 above
Advisory alignment with expert consensus (CEGG)
“Annex C of the Statement” https://www.eyes.nhs.scot/for-professionals/legislation/

* Scottish formularies should be available within the Prescribing section of your Health Board pages on the eyes.nhs.scot website. If unavailable, contact your local Health Board for further information; Health Boards landing page

If you have a query relating to this page, please email NSS.ComEyecareGuidelineGroup@nhs.scot

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