From the Guidelines
Conjunctivitis is primarily caused by viral infections, bacterial infections, allergies, irritants, and certain medical conditions, with the most common causes being adenoviruses, Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae, as well as allergic reactions to pollen, pet dander, or dust mites 1. The causes of conjunctivitis can be classified into several categories, including:
- Infectious conjunctivitis, which can be further divided into viral and bacterial conjunctivitis
- Noninfectious conjunctivitis, which includes allergic, mechanical/irritative/toxic, immune-mediated, and neoplastic types
- Conjunctivitis secondary to systemic or ocular diseases, such as dry eye, blepharitis, and atopy Some specific types of conjunctivitis include:
- Gonococcal conjunctivitis, which is caused by Neisseria gonorrhoeae and can lead to serious complications if left untreated 1
- Chlamydial conjunctivitis, which is caused by Chlamydia trachomatis and can lead to chronic inflammation and scarring 1
- Floppy eyelid syndrome, which is a condition characterized by eyelid swelling and ptosis, and can be associated with sleep apnea and keratoconus 1
- Medication-induced/preservative-induced keratoconjunctivitis, which is caused by the use of certain eye medications and can lead to chronic inflammation and scarring 1 The most effective way to prevent conjunctivitis is through early diagnosis and treatment, as well as prevention of transmission through proper hygiene and vaccination, such as the use of erythromycin ointment to prevent ophthalmia neonatorum and the recombinant zoster vaccine to prevent herpes zoster 1.
From the Research
Causes of Conjunctivitis
- Viral conjunctivitis is the most common overall cause of infectious conjunctivitis, usually not requiring treatment 2, 3
- Bacterial conjunctivitis is the second most common cause of infectious conjunctivitis, with most uncomplicated cases resolving in 1 to 2 weeks 2, 4
- Allergic conjunctivitis is encountered in up to 40% of the population, with itching being the most consistent sign 2, 4
- Conjunctivitis can also be caused by sexually transmitted diseases such as chlamydia and gonorrhea, requiring systemic treatment in addition to topical antibiotic therapy 2
Characteristics of Conjunctivitis
- Viral conjunctivitis typically presents with watery discharge and is more common in adults 4, 3
- Bacterial conjunctivitis typically presents as mucopurulent discharge with the eyelids matted shut and is more common in children 4
- Allergic conjunctivitis typically presents with itching and is treated with topical antihistamines and mast cell stabilizers 2, 4
Diagnosis and Treatment
- A comprehensive history and physical examination can guide diagnosis, but there is no single sign or symptom that accurately differentiates viral from bacterial conjunctivitis 4
- Supportive care options for viral conjunctivitis include artificial tears, cold compresses, and antihistamine eye drops 4
- Topical antibiotics decrease the duration of bacterial conjunctivitis and allow earlier return to school or work, but delayed antibiotic prescribing has been found to have similar symptom control as immediate prescribing 2, 4