present with a red, painful, watery eye The conjunctival injection is usually sectoral Presence of concomitant vesicular lesions in the eyelid region helps raise concern for HSV infection, however skin lesions need not be present Patients with herpes zoster ophthalmicus experience pain, often followed by development of vesicular lesions in the involved dermatome (i.e., ophthalmic division of trigeminal nerve), which is commonly associated with significant lid swelling and pain ( Fig 123.9 ) Corneal involvement may occur to days after skin lesions are seen Airborne or contact allergic conjunctivitis is characterized by hyperacute conjunctival injection associated with watery tearing and a blister-like swelling of the conjunctiva (chemosis) ( Fig 123.10 ) Itching is often a prominent symptom The history may reveal recent exposure to an environmental allergen (e.g., cat dander) Seasonal allergic conjunctivitis, a recurrent reaction to outdoor pollens, typically has a less dramatic onset Patients may have a history of atopy such as allergic rhinitis, asthma, or eczema TABLE 123.1 DIFFERENTIAL DIAGNOSIS OF CONJUNCTIVITIS FIGURE 123.7 Patient with right epidemic keratoconjunctivitis infection Note the lid swelling, red eye, and absence of purulent discharge Patient also has right preauricular adenopathy (not visible) Note the early injection of left eye, representing sequential involvement Clinical Assessment No child should be diagnosed or treated for conjunctivitis without a careful examination Although conjunctivitis is characterized by ocular erythema, not all patients with a red eye have conjunctivitis Various ophthalmic conditions, as well as many systemic processes, can be associated with a red eye One should also be weary of making this diagnosis in a patient with recent ocular trauma Chapter 114 Ocular Trauma outlines the evaluation and differential diagnosis of this finding Signs and symptoms not typically associated with conjunctivitis that should prompt a search for a more serious condition include reduced visual acuity, significant ocular pain and/or photophobia, corneal opacities, and significant foreign-body sensations Fluorescein instillation is recommended to fully evaluate the ocular surface in these cases Characteristic dendritic staining patterns can be seen on the cornea or conjunctiva in herpetic infections ( Fig 123.11 ) Ophthalmic consultation is indicated in suspected HSV ocular disease The clinician should also be wary of making the diagnosis of conjunctivitis in contact lens wearers These patients are at risk for inflammation and ulceration of the cornea known as bacterial keratitis A bacterial corneal ulcer will appear as a white spot in the normally clear cornea associated with conjunctival injection, foreign body sensation or pain, photophobia, and decreased vision (see Chapter 27 Eye: Red Eye ) This is a rapidly progressing sight-threatening condition that requires immediate consultation with an ophthalmologist FIGURE 123.8 Patient with herpes simplex infection limited to the eyelids Conjunctiva appear white/noninjected (absence of corneal and conjunctival involvement should always be confirmed by fluorescein examination) FIGURE 123.9 Herpes zoster ophthalmicus Note the eyelid swelling and the presence of vesicular lesions in a dermatomal distribution Triage Considerations Some forms of infectious conjunctivitis are highly contagious and spread by direct contact with the patient’s secretions or with contaminated objects and surfaces Potential cases of conjunctivitis should ideally be identified in triage and appropriate contact precautions should be initiated Proper hand washing is essential to prevent spread Diagnostic Testing In neonates with purulent conjunctivitis, urgent bacterial Gram stain and cultures should be obtained to look for gram-negative diplococci consistent with gonorrhea Chlamydial studies may also be useful in this age group Conjunctival specimens must contain conjunctival cells from an everted eyelid since chlamydia is an obligate intracellular organism Although various methods of detection exist (e.g., nucleic acid amplification tests, antigen detection methods), chlamydial cultures remain the gold standard for diagnosis Outside the neonatal period a diagnosis of conjunctivitis can generally be made on the clinical features alone Studies to determine a causative organism should be reserved for cases of severe inflammation or chronic or recurrent infections Viral culturing is rarely necessary