Conjunctivitis

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Pathophysiology

The

conjunctiva is a loose connective tissue that covers the surface of the eyeball (bulbar conjunctiva) and reflects back upon itself to form the inner layer of the eyelid (palpebral conjunctiva). It is firmly adhered to the sclera at the limbus, where
it meets the cornea. The accessory lacrimal glands (Kraus and Wolfring), along with goblet cells, are contained within the conjunctiva and are responsible for keeping the eye lubricated. Like any mucous membrane, infectious agents may adhere to overwhelm
the normal defense mechanisms and produce clinical symptoms of redness, discharge, irritation, and possibly photophobia. Viral etiologies are more common than bacterial etiologies.
Conjunctivitis typically is a self-limited process; however, depending on the immune status of the patient and the etiology, conjunctivitis can progress to more severe and sight-threatening infections.

  • Purulent bacterial conjunctivitis in the neonate usually is caused by Neisseria gonorrhoeae. It can be invasive and lead to rapid corneal perforation.

  • Chlamydial conjunctivitis can lead to conjunctival scarring (cicatrix) that can be severe enough to cause lid derangement and ingrown eyelashes.

  • Trachoma is a more chronic, insidious form of Chlamydia trachomatis infection affecting 500 million people worldwide and is considered the leading cause of blindness in the world, approximately 10% of those affected.

  • Chlamydial pneumonia can occur in infants up to 6 months after their conjunctivitis.

  • Three major agents associated with follicular conjunctivitis, preauricular adenopathy, and superficial keratitis are adenovirus, chlamydia, and herpes simplex. Neisseria can be associated with adenopathy but the keratitis is ulcerative and not superficial.
    Many times one can elicit a history of a viral syndrome, sexually transmitted disease, or history of fever blisters, which can help make the diagnosis. Adenovirus is extremely contagious and individuals should be advised to be diligent with hand washing and avoid contact with their tears. Sharing pillows, towels, computer keyboards, and anything in contact with infected secretion helps spread the infection to others.

  • Conjunctivitis of the newborn is the term used by the World Health Organization (WHO) for any conjunctivitis with discharge occurring during the first 28 days of life. Ophthalmia neonatorum was the term previously used to describe a hyperacute purulent conjunctivitis, usually caused by gonococcus, in the first 10 days of life. In this instance, transmission is vertical.

  • Any individual with follicular conjunctivitis, preauricular adenopathy with or without keratitis should be questioned about the possibility of STD; high risk individuals should be treated empirically for chlamydia.

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