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The Ultimate Guide to Conjunctivitis Differential Diagnosis

Nov 10, 2021
101 min read
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“Pink eye” is one of the most common complaints eyecare providers encounter. This is not surprising considering “pink eye” is a catch-all term used to describe red, watery eyes. Likewise, conjunctivitis, the clinical term for “pink eye” is also a broad classification that encompasses many different conditions with varied underlying causes but similar signs and symptoms. Conjunctivitis affects nearly six million people annually in the U.S.1 and accounts for about 1% of all primary care visits and 28% of ER visits.2,3

Clinical presentation

Conjunctivitis specifically refers to the inflammation of the bulbar and palpebral conjunctiva of the eye. This inflammation results in varying degrees of injection and edema, which gives “pink eye” its classic reddish-pink, swollen appearance and is often accompanied by some form of discharge.4 The underlying causes of conjunctivitis vary and include infectious etiologies such as bacterial, viral, fungal, and parasitic infections as well as noninfectious causes like allergies, inflammatory conditions, and mechanical irritation.

Accurately diagnosing the specific cause of conjunctivitis has been shown to be a challenge for providers, as 80% of cases of infectious conjunctivitis are treated with antibiotics, while only 30% of cases are truly bacterial in nature.5 However, while the different forms of conjunctivitis may present in similar fashions, there are key differences, although sometimes subtle, that help differentiate them.

It is critical for eyecare providers (ECPs) to identify these differences quickly and accurately, as the treatments for the various forms of conjunctivitis can differ significantly. Fortunately, there are several hallmark features that make delineating the different causes of conjunctivitis relatively straightforward.

Conjunctivitis can be caused by many underlying factors, but all forms tend to share the basic presentation of red, irritated eyes, with some form of discharge as seen in Figure 1.