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Understanding the Differences: Viral, Bacterial and Allergic Conjunctivitis


Overview

Conjunctivitis is the inflammation of the conjunctiva, which is the mucous membrane lining the inner surface of the eyelid. Usually, this portion of the eye is transparent but when inflamed, it appears pink or red on general examinations. There are several types of acute conjunctivitis (bacterial or viral), noninfectious (allergic or nonspecific) and the types also different based on the population affected. Bacterial conjunctivitis is much more common in pediatric patients while viral is more common within the adult population. 


Bacterial Conjunctivitis

Patients with bacterial conjunctivitis typically have redness and purulent discharge in one eye. The discharge is usually yellow in color and thick. This differs from allergic conjunctivitis which is watery and stringy. The affected eye is often closed in the morning and difficult to open. Bacterial conjunctivitis is usually caused by Staphylococcus aureus (most common in adults), Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis. Bacterial conjunctivitis is highly contagious as it is spread with direct contact. 


Viral Conjunctivitis

Viral conjunctivitis is typically caused by adenovirus. Usually patients have adenopathy, fever, pharyngitis, and upper respiratory tract infection. Viral conjunctivitis, like bacterial, is very contagious due to it being spread by direct contact with secretions or contaminated surfaces. Unlike bacterial conjunctivitis, viral conjunctivitis presents as a conjunctival injection along with water discharge and a sandy or gritty feeling in one eye. Typically, symptoms get worse over the first three to five days with resolution over one to two weeks. 


Allergic Conjunctivitis

Allergic conjunctivitis is due to airborne allergens contacting the eye that cause an IgE-mediated hypersensitivity response and cause local mast cell degranulation and release of chemical mediators (histamine, eosinophil chemotactic factors, and platelet-activating factors). Typically patients experience bilateral redness, watery discharge, and itching. Although viral conjunctivitis presents similarly, it will not have the itching as in allergic conjunctivitis and instead has the burning or gritty sensation. 


Other Types of Conjunctivitis

Nonspecific conjunctivitis is when a patient develops a red eye and discharge not related to an infectious or inflammatory process. The typical cause is a transient mechanical or chemical insult. 


Treatment

When exploring treatment options, it is important to distinguish between the different types of conjunctivitis. Cultures and stains are not needed for diagnosis, as this is done mainly through clinical evaluation. Only patients with bacterial conjunctivitis should be receiving antibiotics such as erythromycin ointment or trimethoprim-polymyxin B drops. Patients who wear contact lenses are at higher risk for keratitis with co-infection Pseudomonas aeruginosa and should instead be prescribed fluoroquinolones. Patients with viral conjunctivitis should only be given agents for symptomatic relief. These include topical antihistamines and decongestants such as naphazoline-phenriamine. In addition, they should be using warm compresses to reduce discharge and crusting on eyelids. Patients with allergic conjunctivitis should also start an antihistamine and decongestant regimen. Those with noninfectious conjunctivitis should seek symptom relief with topical lubricants such as over-the-counter drops or ointments. Patients should be wary of lubricant drops as they have the ability to cause blurry vision and should only be used before bed. 



Warning signs for urgent ophthalmology referral include but are not limited to: reduced visual acuity, ciliary flush, photophobia, severe foreign body sensation, corneal opacity, fixed pupil and severe headache. It is important to prevent the spread of both viral and bacterial conjunctivitis, since these are highly contagious. This includes not sharing clothing, towels, cosmetics, linens or utensils. Since bacterial and viral conjunctivitis are highly contagious, patients should stay home until there is no discharge from their eyes. Most daycare and schools require 24 hours of topical therapy before returning to school. The topical therapy is only effective with bacterial conjunctivitis and not viral conjunctivitis. Prevention is important to prevent the spread and includes proper hand washing with soap and water or alcohol based rubs. As summer ends and fall begins, infection rates will start to climb. It is important to understand the differences between each type of conjunctivitis and treat them effectively.



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