• Clinical science

Keratitis

Abstract

Keratitis is inflammation of the cornea, a clear and transparent covering over the iris and pupil. Important forms of keratitis include bacterial, herpes zoster, herpes simplex, and Acanthamoeba keratitis. Most corneal injuries and infections are associated with severe pain, although sometimes pain is absent. Other findings include irritation, eye redness, watery or purulent secretion, and impaired vision. Diagnosis is usually based on clinical findings and slit-lamp examination. Keratitis is an emergent disorder that can lead to irreversible vision loss left untreated.

Overview

Characteristic features Therapy
Bacterial keratitis
  • Most common form of keratitis
  • ↑ Risk with wearing contact lenses
  • Purulent discharge and/or hypopyon
  • Round corneal infiltrate or ulcer
Herpes zoster keratitis
  • ↓ Corneal sensation
  • Punctate lesions on the corneal surface (early disease)
  • Vesicular eruption on forehead, bridge, and tip of the nose
Herpes simplex keratitis
  • Dendritic or geographic corneal ulcer
Acanthamoeba keratitis
  • ↑ Risk with wearing contact lenses
  • Corneal ring infiltrate
  • Topical antiseptic (e.g., chlorhexidine) with propamidine

Bacterial keratitis

Bacterial keratitis should be treated as an ophthalmic emergency because of the risk of irreversible vision loss!

References:[1][2][3][4][5][6]

Viral keratitis

Herpes simplex keratitis

  • Etiology: infection due to reactivated herpes simplex virus (HSV) type 1 from the trigeminal ganglion
  • Clinical features
    • Similar to viral conjunctivitis, but usually unilateral
    • Eye redness
    • ± Eye pain
    • Foreign body sensation
    • Photophobia
    • Blurry vision; can lead to vision loss if untreated
  • Diagnostics
    • Fluorescein staining: superficial corneal erosions (dendritic ulcers) that resemble the branches of a tree (geographic ulcers may be seen when dendritic ulcers widen in shape)
    • Direct fluorescein antibody test (HSV antigen detection) or polymerase chain reaction (PCR) test
  • Treatment for epithelial HSV keratitis
    • Topical trifluridine ; solution or ganciclovir 0.15% gel
    • Oral antiviral (e.g., acyclovir) when topical treatment cannot be administered; by the patient, prophylactic treatment after surgery, or refractory cases despite topical treatment
    • Corneal transplantation for patients with severe corneal scarring

Glucocorticoids should not be used in initial treatment of dendritic epithelial keratitis!

Herpes zoster keratitis

  • Etiology: reactivated herpes zoster virus (involvement of the ophthalmic nerve ); see also herpes zoster ophthalmicus.
  • Clinical features
    • Prodrome: headache, malaise, fever
    • Impaired vision
    • Eye irritation (foreign body sensation)
    • Photophobia
    • Eye pain
    • In the innervation area of the ophthalmic nerve (forehead, bridge, and tip of the nose):
      • Vesicular eruption
      • Anesthesia dolorosa
  • Diagnosis
    • Slit-lamp examination and fluorescein staining
      • 1–2 days: punctate lesions on the corneal surface
      • 4–6 days: dendritic lesions on the corneal surface
      • 1–2 weeks: stromal infiltrates below the corneal surface
      • Months to years: deep stromal infiltrates and neovascularization or corneal ulcers
  • Treatment: oral acyclovir, valacyclovir, or famciclovir
  • See also herpes zoster ophthalmicus.

Adenovirus

See epidemic keratoconjunctivitis.

References:[7][8][9][10][11][12][13][14]

Acanthamoeba keratitis

  • Etiology: Acanthamoeba infection
  • Characteristics
    • Rare condition
    • Primarily occurs in immunocompetent contact lens wearers
    • Progressive course for several weeks despite an attempt of antibiotic treatment
  • Clinical features
    • Severe pain
    • Eye redness
    • Photophobia
    • Epiphora
    • Decrease in vision
    • Corneal ring infiltrate (late-stage)
  • Diagnostics
    • Slit-lamp examination and/or fluorescein staining: features of epithelitis and stromal disease
    • Culture and microscopy of eye scraping
    • Pathogen detection is often difficult.
      • Solid histological evidence of amebae cysts in excised corneal material
      • Immunofluorescence is often negative.
      • Microbiological examination of the contact lens to determine the causative pathogen
  • Treatment
    • Topical antiseptic (e.g., chlorhexidine) with propamidine
    • Corneal transplantation for refractory cases: penetrating keratoplasty

References:[15][16]

Fungal keratitis

References:[6981][17][18][19]

Non-infectious keratitis

Exposure keratopathy

  • Definition: keratitis caused by the inability to completely close the eyelids resulting in corneal drying
  • Etiology: mainly caused by damage to the facial nerve, e.g., from a stroke

Neurotrophic keratopathy

  • Definition: keratitis as a result of corneal sensory loss due to paralysis of the 1st trigeminal branch
  • Etiology
  • Clinical features
    • Decreased vision; dry eye
    • Early stage: absent corneal reflex; decreased tear break-up time; dry spots on corneal surface
    • Late stage: central circular/oval nonhealing corneal ulcer
    • Complication: corneal perforation
  • Treatment
    • Early stage: artificial tears
    • Late stage: prophylactic antibiotic drops; tarsorrhaphy ; amniotic membrane transplantation and conjunctival flap

Photokeratitis

  • Definition: corneal epithelial damage caused by severe UV light radiation with pronounced pain symptomatology
  • Etiology
    • Welding without proper protective eye wear
    • Associated with cosmetic tanning (tanning bed)
    • High levels of UV radiation in high-altitude mountain regions
  • Pathophysiology
  • Clinical features
  • Diagnostics
    • Bilateral multiple, fine-spotted, superficial, fluorescein-positive corneal epithelial lesions (Thygeson superficial punctate keratopathy)
    • Conjunctival vessel injection
  • Treatment:
    • Patient briefing
    • Antibiotic eye ointment
    • Immobilization
    • Oral analgesics
  • Course:

Anesthetic eye drops should only be applied for diagnostic purposes! Do not initiate pain therapy as improper use can lead to epithelial damage. Elimination of the protective corneal reflex can result in further corneal damage!