MODEL RELEASED. General practice doctor swabs the eye of a young child suffering conjunctivitis. The cotton swab is used to collect a sample of fluid which will be analysed in the laboratory to determine the cause of infection . Conjunctivitis is the inflammation of the conjunctiva, the surface layer of mucous membrane that covers the front of the eye. The conjunctiva may become red and swollen, and it produces a watery or pus- containing discharge. Vision is seldom affected. Conjunctivitis is usually caused by bacterial infection (e.g. staphylococci).