Pr Eric E. GabisonOphthalmology · Cornea & refractive · Paris
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Home › Pro area › Infectious keratitis › Synthesis & references
Course contents ▾
  1. Introduction & epidemiology
  2. Pathophysiology
  3. Examination & semiology
  4. Severity criteria
  5. Bacterial — overview
  6. Gram-positive cocci
  7. Bacilli & atypical
  8. Fungal keratitis
  9. Acanthamoeba keratitis
  10. Low-risk — empirical
  11. Microbiology & sampling
  12. Targeted therapy & surgery
  13. Synthesis & algorithm
  14. References
Chapitre 13

Synthesis & decision algorithm

The reasoning proceeds in four steps.

Algorithm

1. Every abscess → history (risk factors) + slit lamp/fluorescein + systematic description + assessment of severity criteria (1-2-3 rule).

2. Low-risk bacterial → empiric antibiotic therapy (hourly fluoroquinolone), reassessment at 48 h, no steroids.

3. Severity criterion, non-bacterial appearance, or worsening at 48 h → scraping + sampling (direct examination, culture, PCR, ± confocal) → fortified drops (bacterial), antifungals or anti-amoebics as indicated → adapt to susceptibility testing.

4. Adjuncts & escalation → PACK-CXL (bacterial/fungal), intrastromal injections; cautious and late steroids; surgery (hot graft, amniotic membrane) for failure or perforation.

Key messages

  • The clinical appearance guides but does not identify the organism — sampling directs treatment of severe forms.
  • Disproportionate pain + contact lenses + resistant "herpes" = amoeba until proven otherwise.
  • Fungal keratitis: think vegetal trauma and sample the base of the abscess; steroids = danger.
  • The size of the infiltrate measures the response; the size of the epithelial defect measures toxicity.
  • Rising fluoroquinolone resistance (ARMOR, BOSS): regularly reassess empiric protocols.
Chapitre 14

References

  1. Ting DSJ, Ho CS, Deshmukh R, Said DG, Dua HS. Infectious keratitis: an update on epidemiology, causative microorganisms, risk factors, and antimicrobial resistance. Eye (Lond). 2021;35(4):1084–1101.
  2. Ung L, Bispo PJM, Shanbhag SS, Gilmore MS, Chodosh J. The persistent dilemma of microbial keratitis: global burden, diagnosis, and antimicrobial resistance. Surv Ophthalmol. 2019;64(3):255–271.
  3. Zimmerman AB, Nixon AD, Rueff EM. Contact lens associated microbial keratitis: practical considerations for the optometrist. Clin Optom (Auckl). 2016;8:1–12.
  4. Ting DSJ, Ho CS, Cairns J, Elsahn A, Al-Aqaba M, Boswell T, et al. 12-year analysis of incidence, microbiological profiles and in vitro antimicrobial susceptibility of infectious keratitis: the Nottingham Infectious Keratitis Study. Br J Ophthalmol. 2021;105(3):328–333.
  5. Cabrera-Aguas M, Khoo P, Watson SL. Antimicrobial resistance in ocular infection: a review. Clin Exp Ophthalmol. 2024. doi:10.1111/ceo.14377.
  6. Khor WB, Prajna VN, Garg P, Mehta JS, Xie L, Liu Z, et al. The Asia Cornea Society Infectious Keratitis Study: a prospective multicenter study of infectious keratitis in Asia. Am J Ophthalmol. 2018;195:161–170.
  7. Dalmon C, Porco TC, Lietman TM, Prajna NV, Prajna L, Das MR, et al. The clinical differentiation of bacterial and fungal keratitis: a photographic survey. Invest Ophthalmol Vis Sci. 2012;53(4):1787–1791.
  8. Brown L, Leck AK, Gichangi M, Burton MJ, Denning DW. The global incidence and diagnosis of fungal keratitis. Lancet Infect Dis. 2021;21(3):e49–e57.
  9. Prajna NV, Krishnan T, Mascarenhas J, Rajaraman R, Prajna L, Srinivasan M, et al. The Mycotic Ulcer Treatment Trial: a randomized trial comparing natamycin vs voriconazole (MUTT I). JAMA Ophthalmol. 2013;131(4):422–429.
  10. Prajna NV, Krishnan T, Rajaraman R, Patel S, Srinivasan M, Das M, et al. Effect of oral voriconazole on fungal keratitis in the Mycotic Ulcer Treatment Trial II (MUTT II). JAMA Ophthalmol. 2016;134(12):1365–1372.
  11. Dart JKG, Papa V, Rama P, et al. The Orphan Drug for Acanthamoeba Keratitis (ODAK) trial: PHMB 0.08% (polihexanide) and placebo versus PHMB 0.02% and propamidine 0.1%. Ophthalmology. 2024;131(3):277–287.
  12. Robaei D, Carnt N, Minassian DC, Dart JKG. The impact of topical corticosteroid use before diagnosis on the outcome of Acanthamoeba keratitis. Ophthalmology. 2014;121(7):1383–1388.
  13. Ting DSJ, Henein C, Said DG, Dua HS. Photoactivated chromophore for infectious keratitis — corneal cross-linking (PACK-CXL): a systematic review and meta-analysis. Ocul Surf. 2019;17(4):624–634.
Warning

Concentrations, dosages, and thresholds are given as literature reference points, to be individualized and verified before any prescription. Labels and references to be cross-checked on PubMed before distribution.