Causes
Several studies show that acute conjunctivitis occurs with almost equal frequency between bacterial and viral causes Mucopurulent conjunctivitis

is caused by bacterial organisms.

  • Gram-positive for the following cocci: Staphylococcus epidermidis, Streptococcus pyogenes, and Streptococcus pneumoniae

  • Gram-negative for the following cocci: Neisseria meningitidis and Moraxella lacunata

  • Gram-negative

    for the following rods: genus Haemophilus and family Enterobacteriaceae Hyperpurulent conjunctivitis usually is caused by N gonorrhoea.

  • N gonorrhoea, Chlamydia trachomatis, and bacteria (mainly Staphylococcus species and S pneumoniae) cause conjunctivitis of the newborn.

    • Approximately 90% of infants receiving Crede prophylaxis for gonorrheal ophthalmic (silver nitrate application) experience a mild transient conjunctival injection and tearing with variable purulence that typically resolves in 24-48 hours.

  • Many types of viruses, most commonly adenovirus, cause viral conjunctivitis.

  • Atopic conjunctivitis typically occurs in male teenagers who have a history of childhood atopic dermatitis. It resembles vernal conjunctivitis but is not seasonal.

  • Vernal conjunctivitis is a bilateral recurrent hypersensitivity that occurs during the warm months of the year, particularly in hot climates.

  • Giant papillary conjunctivitis predominantly is associated with contact lens wear.

  • Toxic conjunctivitis occurs with airborne irritants or a direct splash of liquid or powder to the eye.

  • Unusual causes may be considered in patients with atypical presentations, including parasitic (eg, Loa loa, Trichinella, Onchocera), autoimmune (sicca, pemphigoid), and systemic diseases (sarcoidosis, tuberculosis, Reiter syndrome, Kawasaki disease)