Infectious Conjunctivitis: Types, Pathogens, and Signs

Conjunctivitis is inflammation of the conjunctiva, the thin transparent membrane that covers the white of the eye and lines the eyelids. Inflammation occurs due to infection, allergy, or irritation. Infectious conjunctivitis is caused by viruses and bacteria.

What infectious conjunctivitis is

Tears protect the eye: they wash away microbes and irritants, and proteins and antibodies in tears kill pathogens. If the eyes are too dry, the protection weakens, and it is easier for microbes to cause inflammation. Most often conjunctivitis is caused by viruses and bacteria. "Pink eye" usually means a viral infection that spreads easily among children. Conjunctivitis can appear in a person with coronavirus disease even before other typical symptoms. In newborns, the eye can become infected by bacteria from the mother's birth canal, and this condition requires immediate treatment to preserve vision.

Bacterial and viral conjunctivitis: how they differ

In adults, about 85 percent of conjunctivitis cases are caused by adenoviruses and only 15 percent by bacteria. In children, bacterial and adenoviral forms occur equally often. The virus is transmitted by airborne droplets and causes outbreaks in kindergartens and schools. The bacterial form is caused by pyogenic bacteria: staphylococci, streptococci, pneumococci, gonococci, the Koch-Weeks bacillus, and the Morax-Axenfeld bacillus. Gonococcal, or blennorrheal, conjunctivitis occurs in newborns when passing through the birth canal of a mother with gonorrhea. Some sexually transmitted infections also cause conjunctivitis, and this form takes longer to heal.

Follicular and angular conjunctivitis

With adenoviral infection, follicles or films often appear, more often in children; this picture is called follicular conjunctivitis. Angular conjunctivitis is caused by the Morax-Axenfeld bacillus: it runs a subacute or chronic course and is located mainly in the corners of the palpebral fissure.

How infectious conjunctivitis manifests

One or both eyes may be affected: they become red, burn, and there is a sensation of sand, itching, lacrimation, photophobia, and swelling of the eyelids. In the bacterial form, there may be viscous gray or yellowish discharge, because of which the eyelids stick together after sleep; sometimes the only sign is a feeling of a foreign body and dryness of the eye and the skin around it. The viral form starts in one eye and passes to the other, often against the background of a cold and sore throat, with enlargement of the preauricular lymph nodes. Conjunctivitis with sticky pus is contagious.

• Redness and burning in both eyes.
• Eyelids stuck together after sleep in the bacterial form.
• Lacrimation and photophobia in the viral form.
• Follicles or films on the conjunctiva, more often in children.
• Dryness of the eye and the skin around it.

How a doctor determines the type and pathogen

The doctor examines the eyes and, if necessary, takes a swab from the conjunctiva for analysis. There are tests that can identify the specific virus. Based on the results of the examination and analysis, it is determined whether the form is viral, bacterial, or another, because the cause determines whether antibacterial treatment should be prescribed: in the viral and allergic forms it does not work.

When to see an ophthalmologist

You should see a doctor if symptoms do not resolve within 7 days, vision has changed, photophobia has appeared, there is severe or increasing pain in the eye, swelling or redness of the eyelids and skin around the eyes, or headache. If you wear contact lenses and spots have appeared on the eyelids, an allergy to the lenses is possible. An infant younger than 30 days with red sticky eyes needs an urgent doctor's appointment.

Redness of the eyes alone is not a reason to call an ambulance; 103 or 112 — if the condition has sharply worsened and the person needs emergency care.

This material is for reference: it helps to understand the names of the types of conjunctivitis, but does not replace consultation with a doctor, who will examine the eye and determine the pathogen.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer