Keratitis describes inflammation of the cornea. Microbial keratitis is not like conjunctivitis - it is potentially sight threatening and should therefore be urgently evaluated and treated.

Aetiology

• bacterial
  • typically Staphylococcus aureus
  • Pseudomonas aeruginosa is seen in contact lens wearers
• fungal
• amoebic
  • acanthamoebic keratitis
  • accounts for around 5% of cases
  • increased incidence if eye exposure to soil or contaminated water
• parasitic: onchocercal keratitis ('river blindness')

other factors that may causes keratitis:

• viral: herpes simplex keratitis
• environmental
  • photokeratitis: e.g. welder's arc eye
  • exposure keratitis
  • contact lens acute red eye (CLARE)

PC

• red eye: pain and erythema
• photophobia
• foreign body, gritty sensation
• hypopyon may be seen

Investigations

Under slit lamp examination with fluorescein applied, dendritic ulcers may be seen, which are pathognomonic of the infection.