Because infections of the surface of the eye are common, and the consequences of misdiagnosis or delayed referral may be severe, familiarity with the anatomy and variable presentations of these infections is crucial to the acute care physician. The conjunctiva is a well-vascularized, clear membrane that both envelops the globe and wraps underneath the eyelids (Figure 30.1). The former segment is labeled the bulbar conjunctiva, and the latter, the tarsal or palpebral conjunctiva. The conjunctiva, along with the tear film, provides a physical and immunologic barrier against microbes and can produce an antimicrobial environment when its mast cells are activated.
Just below the conjunctiva is the vascularized episclera, and beneath this the sclera, which lies just over the choroid. The choroid and the episclera provide oxygen to the poorly vascularized sclera.
The cornea itself is subject to inflammation, which can be due to noninfectious causes (noninfectious keratitis) or infectious causes (infectious keratitis, including that caused by bacteria, viruses, or fungi).
Of all red-eye complaints, conjunctivitis (Figure 30.2) is the most common diagnosis. It can be separated into three categories: bacterial, viral, and allergic (Table 30.1).
Conjunctivitis is diffuse, not localized. Localized hyperemia may suggest:
Conjunctivitis should inflame both the bulbar and tarsal conjunctiva.