CausesSeveral 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)
