Bacterial keratitis

Bacterial keratitis is also often referred to as a corneal ulcer, although these terms are not directly interchangeable because a cornea may harbor a bacterial infection (i.e bacterial keratitis) without having a loss of tissue (an ulcer), and a cornea may have an ulcer without a bacterial infection.

Background

• Rapidly progressing, with corneal destruction as fast as within 24 hrs
• Corneal perforation is most sight threatening complication
• Strep, staph, pseudomonas, enterobacteriaceae
• Risk factors
  • Contact lens use
  • Corneal surgery, trauma
  • Chronic dry eye
  • Recent corneal disease (viral, fungal keratitis)
  • Immune deficiency, topical steroids

Clinical Features

Bacterial keratitis due to Pseudomonas spp.

• Blurred vision
• Severe pain and photophobia
• Perilimbic injection
• Normal pupil size
• Eyelid edema
• Mucopurulent exudate
• Posterior synechiae (iris adheres to cornea)

Differential Diagnosis

• Iritis
• Conjunctivitis
• Glaucoma
• UV keratitis
• Herpes zoster
• Contact lens complication
• Fungal keratitis
• Bacterial keratitis
• Interstitial keratitis
• Herpes keratitis
• Endophthalmitis

Evaluation

• Topical anesthesia with proparacaine, as opposed to tetracaine which has bacteriostatic effects, limiting culture results
• Culture and gram stain of corneal ulcer edges, eyelids, conjunctiva, contact lenses
• Ultrasound to assess for signs of endophthalmitis and other pathologies

Management

• Broad spectrum topical antibiotics; 1 drop q1 hr
  • Tobramycin 14mg/ml
  • Alternate with fortified cefazolin 50mg/ml
• Smaller corneal ulcers may be treated with moxifloxacin or gatifloxacin ophthalmic

Disposition

• Ophtho consult for possible perforation risk
• Eye patch in the interim

References

• Murillo-Lopez F et al. Bacterial Keratitis. Aug 24, 2014. http://emedicine.medscape.com/article/1194028-overview.