Periorbital cellulitis is a common and serious infection that affects the tissues around the eye. Understanding its causes is important for prevention and prompt medical attention. This condition involves bacterial infiltration, leading to inflammation and swelling in the affected area.
Understanding Periorbital Cellulitis
Periorbital cellulitis, also known as preseptal cellulitis, refers to an acute infection of the eyelid and the soft tissues surrounding the eye. This infection is located anterior, or in front of, the orbital septum, a thin fibrous membrane that acts as a barrier within the eye socket. It is important to distinguish periorbital cellulitis from orbital cellulitis, a more severe infection affecting tissues deeper behind this septum.
Individuals with periorbital cellulitis experience sudden onset of redness, swelling, and tenderness around one eye. The affected area may also feel warm to the touch. Unlike orbital cellulitis, periorbital cellulitis does not affect vision or cause pain with eye movement, and the eyeball itself appears normal.
Primary Microbial Culprits
The primary agents responsible for periorbital cellulitis are bacteria. The most frequently identified bacterial species include Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus pneumoniae. Staphylococcus aureus can also include methicillin-resistant strains, known as MRSA.
Historically, Haemophilus influenzae type b (Hib) was a common cause of periorbital cellulitis, particularly in young children. However, widespread vaccination against Hib has dramatically reduced its prevalence, making it a much rarer cause today. While bacteria are the predominant cause, fungal infections can also occur, especially in individuals with compromised immune systems.
Pathways of Infection
Microorganisms primarily gain entry to the periorbital tissues through several common routes. One frequent pathway involves breaks in the skin barrier around the eye, such as those caused by insect bites, minor cuts, abrasions, or chickenpox lesions. These skin disruptions provide an opening for bacteria to enter and establish an infection.
Infections can also spread from nearby areas through contiguous dissemination. This includes local infections like impetigo (a skin infection), styes, or conjunctivitis (pink eye). Another pathway is the extension of infection from adjacent structures, particularly the paranasal sinuses. Ethmoid sinusitis, due to its close anatomical proximity to the eye socket, is a common source of spread. Less commonly, dental infections can also serve as a source for bacterial spread to the periorbital area.
Predisposing Factors
Several factors can increase an individual’s susceptibility to developing periorbital cellulitis. Age is a significant factor, with the condition being more prevalent in young children, especially those aged 5 or younger. Children are more susceptible due to their developing immune systems and higher rates of upper respiratory tract infections.
Compromised immune systems, resulting from conditions like diabetes, certain medications, or chemotherapy, can also increase vulnerability to infection. Individuals with pre-existing skin conditions, such as eczema, may have a compromised skin barrier, making them more prone to bacterial entry. Recent upper respiratory tract infections, including colds or sinusitis, are associated with periorbital cellulitis, as these can provide a source for bacterial spread.