What differentiates viral conjunctivitis from bacterial conjunctivitis?

From the Guidelines

Distinguishing between viral and bacterial conjunctivitis is crucial, as viral conjunctivitis typically presents with watery discharge, mild redness, and often affects both eyes, whereas bacterial conjunctivitis produces thick, yellow-green discharge, intense eye redness, and may affect one or both eyes, with more severe discomfort and crusting 1. The key differences between viral and bacterial conjunctivitis lie in their clinical signs, associated factors, natural history, and potential sequelae. Viral conjunctivitis, such as that caused by Herpes simplex virus (HSV) or Varicella zoster virus (VZV), usually presents with unilateral or bilateral bulbar conjunctival injection, watery discharge, and mild follicular reaction of the conjunctiva, with distinctive signs including vesicular rash or ulceration of the eyelids and pleomorphic or excavated dendritic epithelial keratitis of the cornea 1. Some key points to consider when differentiating between viral and bacterial conjunctivitis include:

• Clinical signs: viral conjunctivitis typically presents with watery discharge, mild redness, and often affects both eyes, whereas bacterial conjunctivitis produces thick, yellow-green discharge, intense eye redness, and may affect one or both eyes.
• Associated factors: viral conjunctivitis is often associated with cold symptoms, swollen lymph nodes near the ears, and may be triggered by stress, other acute viral or febrile illnesses, ultraviolet exposure, surgery, or trauma, whereas bacterial conjunctivitis may be associated with oculogenital spread, immunosuppression, or sexual abuse in children.
• Natural history: viral conjunctivitis usually subsides without treatment within 1-2 weeks, whereas bacterial conjunctivitis often improves within 2-5 days with antibiotic treatment.
• Potential sequelae: viral conjunctivitis may lead to complications such as blepharitis, epithelial keratitis, corneal edema, endotheliitis, stromal keratitis, neovascularization, scarring, thinning, perforation, uveitis, trabeculitis, or retinitis, whereas bacterial conjunctivitis may lead to corneal infection, corneal scarring, corneal perforation, urethritis, pelvic inflammatory disease, septicemia, or arthritis. It is essential to seek medical attention promptly if symptoms worsen or do not improve, as a healthcare provider can perform specific tests to confirm the diagnosis and recommend appropriate treatment, which may include antibiotic eye drops or ointment for bacterial infections or supportive care for viral infections 1.

From the Research

Differentiation of Viral and Bacterial Conjunctivitis

The differentiation between viral and bacterial conjunctivitis can be challenging, as there is no single sign or symptom that accurately distinguishes between the two 2. However, some key differences can be identified:

• Viral conjunctivitis is the most common overall cause of infectious conjunctivitis and usually does not require treatment 3.
• Bacterial conjunctivitis is the second most common cause of infectious conjunctivitis, with most uncomplicated cases resolving in 1 to 2 weeks 3.
• Mattering and adherence of the eyelids on waking, lack of itching, and absence of a history of conjunctivitis are the strongest factors associated with bacterial conjunctivitis 3.
• Viral and allergic conjunctivitis are more common in adults and typically present with watery discharge, whereas bacterial conjunctivitis is more common in children and typically presents as mucopurulent discharge with the eyelids matted shut 2.

Diagnostic Approach

A comprehensive history and physical examination can guide diagnosis 2. The following factors can be considered:

• Presence of mucopurulent discharge, which is more commonly associated with bacterial conjunctivitis 4, 3.
• Itching, which is a common symptom of allergic conjunctivitis 3, 2.
• History of conjunctivitis, which can help differentiate between viral and bacterial causes 3.
• Presence of other symptoms, such as fever, headache, or fatigue, which can be associated with viral or bacterial infections 5, 6.

Treatment Approach

The treatment approach for conjunctivitis depends on the underlying cause:

• Viral conjunctivitis: supportive care options, such as artificial tears, cold compresses, and antihistamine eye drops 2.
• Bacterial conjunctivitis: topical antibiotics can decrease the duration of the infection and allow earlier return to school or work 5, 4, 3.
• Allergic conjunctivitis: topical antihistamines with mast cell-stabilizing activity are the treatment of choice 3, 2.