Eye infections are serious infections because loss of vision may occur. Eye infections are named for their anatomical site, i.e. conjunctivitis affects the conjunctiva, uveitis affects the uveal tract (iris, ciliary body, choroid, and retina), and endophthalmitis affects the vitreous or aqueous humor that occupies most of the space within the eye. Adjacent structures can be involved in which case the compound names are used such as keratoconjunctivitis and chorioretinitis.
Most eye infections are caused by bacteria and viruses, although some fungal and parasitic infections occur as well. Some symptoms associated with eye infections, e.g., “a red eye,” can be caused by other diseases such as autoimmune uveitis, acute angle glaucoma, and traumatic corneal ulcer.
Conjunctivitis is typically caused by an infection of the conjunctiva but allergic and chemical conjunctivitis also occur. It is useful to consider infectious conjunctivitis according to the age of the patient, namely neonatal conjunctivitis (from birth to 4 weeks of age) and adult conjunctivitis (older children to older adults) separately as the mode of acquisition and the types of causative microbes differ.
Ophthalmia neonatorum is another name for neonatal conjunctivitis caused by either Neisseria gonorrhoeae or Chlamydia trachomatis. The original use of the term” ophthalmia neonatorum” referred to gonococcal conjunctivitis but current common usage includes chlamydial conjunctivitis as well.
Trachoma is the world’s leading cause of preventable blindness. It is a conjunctivitis caused by certain strains of C. trachomatis. Because of its importance, it is discussed separately in the next section.
In neonatal conjunctivitis, the bacteria or viruses are acquired during passage through the birth canal. The neonatal infection is acquired from a mother who either has a symptomatic infection or who is an asymptomatic shedder of the organism.
In adult conjunctivitis, the bacteria or viruses are acquired either by direct contact with infected individuals or by fomites (inanimate objects such as towels) that carry the microbe. A common mode of transmission is a finger that contacts infected secretions and transfers the organism to the eye. Other risk factors include contact lens use and swimming in under-chlorinated pools.
The most characteristic clinical manifestations are a red eye (hyperemia) and a discharge. When the red eye manifests as visibly enlarged blood vessels, the eye is said to be “injected.”) The discharge in bacterial conjunctivitis, such as gonococcal conjunctivitis, is typically copious and purulent (see Figures 80–1 and 80–2), whereas in chlamydial conjunctivitis it is less copious and watery (see Figure 80–3). Gonococcal conjunctivitis can be very severe and cause corneal ulceration, scarring, and blindness. Itching, lid edema, and light sensitivity are additional symptoms of conjunctivitis.
Gonococcal conjunctivitis in neonate (ophthalmia neonatorum). Note purulent exudate in medial aspect of ...