Keratitis

Keratitis is a term that refers to inflammation of the cornea and is an ocular emergency. This may result from a variety of bacterial, viral or fungal infections, or may be non-infective, for example due to trauma or associated with an auto-immune disease.

Inflammation of the cornea commonly presents as

• a painful red eye with reduced visual acuity due to cellular infiltration and later, corneal oedema
• blood vessel dilatation is typically concentrated around the limbus - circumcorneal injection
• often, the conjunctiva is also inflamed - keratoconjunctivitis
• discharge is usually present and may be watery, mucoid or purulent; notably, it is absent in keratoconjunctivitis sicca
• pupil may be small due to reflexive miosis; photophobia is common
• fluorescein readily demonstrates any ulceration (an epithelial breach)

Keratitis an cause significant loss of vision from (1):

• scarring
• astigmatism

Complications leading to blindness (2)

• corneal perforation,
• choroidal detachment
• endophthalmitis,
• phthisis

Corneal ulceration is an ophthalmologic emergency.

• the cause must be identified before treatment starts since some therapies are beneficial in one circumstance but are aggravating in another
• refer the same day for urgent ophthalmological review as delay in treatment may result in loss of sight.

Notes:

• corneal ulceration may occur without keratitis e.g. when a corneal ulcer is secondary to trauma
• non-infective keratitis may occur in autoimmune diseases.
• risk factors include for development of keratitis include:
  • tear insufficiency,
  • malnutrition,
  • Vitamin A deficiency
    • Vitamin A in combination with zinc maintains conjunctival and corneal surfaces (3)
  • contact lens use
• microbial keratitis is an ophthalmological emergency which may lead to loss of vision (4)
  • a Japanese study revealed that (5):
    • causative agents of microbial keratitis were
      • gram-positive bacteria (commonest)
      • gram-negative bacteria
      • fungi; and
      • acanthamoeba
    • contact lens wear was the most common risk factor for development of microbial keratitis in this study

Reference:

1. Tuli SS, et al. Ocul Surf. 2007 Jan;5(1):23-39. Science and strategy for preventing and managing corneal ulceration.
2. Whitcher JP et al. Corneal blindness: a global perspective. Bulletin of the World Health Organization, 2001; 79 (3).
3. Heinz C, et al.Corneal perforation associated with vitamin-A-deficiency. Ophthalmologe. 2004; 101(6):614-7.
4. Curr Opin Infect Dis. 2007 Apr;20(2):129-41
5. Toshida H et al. Trends in microbial keratitis in Japan.Eye Contact Lens. 2007 Mar;33(2):70-3