Orbital cellulitis is a serious infection that affects the tissues located behind the orbital septum, which is a thin membrane separating the eyelid from the eye socket. This infection involves the fat and muscles within the eye socket and can rapidly become dangerous if not treated promptly. The primary cause of orbital cellulitis is the spread of bacteria from nearby infections, most commonly from the sinuses.
The most frequent origin of orbital cellulitis is **sinusitis**, particularly infections of the ethmoid sinuses, which lie adjacent to the orbit. When these sinuses become infected, bacteria can break through the thin bony walls separating the sinuses from the orbit and invade the orbital tissues. This leads to inflammation, swelling, and infection within the orbit. The bacteria responsible for this are often those that normally colonize the upper respiratory tract, such as *Streptococcus pneumoniae* and *Streptococcus pyogenes*. These bacteria have specific surface structures that allow them to invade tissues and trigger a strong inflammatory response, which contributes to tissue damage in the orbit.
Another common bacterial culprit is *Staphylococcus aureus*, which frequently causes skin infections. This bacterium can spread from infections on the skin around the eye or face into the orbit. *Staphylococcus aureus* produces toxins that enhance its ability to cause inflammation and tissue destruction, making the infection more severe.
Besides sinus infections and skin infections, orbital cellulitis can also arise from other sources:
– **Trauma to the eye or orbit**, such as injuries or surgical procedures, can introduce bacteria directly into the orbital tissues.
– **Dental infections** or infections of the middle ear can spread to the orbit through connected anatomical pathways.
– **Bloodstream infections** can also seed bacteria into the orbital tissues, especially in individuals with weakened immune systems.
The infection causes the tissues in the orbit to become inflamed and swollen, leading to symptoms such as severe pain (especially when moving the eye), bulging of the eye (proptosis), restricted or painful eye movements, fever, and sometimes vision changes or loss. The inflammation and swelling can compress important structures like the optic nerve, which can threaten vision.
Certain bacteria involved in orbital cellulitis may be resistant to common antibiotics, such as methicillin-resistant *Staphylococcus aureus* (MRSA). This resistance can complicate treatment and requires careful selection of antibiotics.
Preventing orbital cellulitis involves early and effective treatment of sinus infections, skin infections around the eye, dental infections, and ear infections before they can spread. Prompt medical attention to any infection near the eye is crucial to avoid progression to orbital cellulitis.
In summary, orbital cellulitis is caused primarily by bacterial infections spreading from adjacent sinuses, skin, or other nearby structures into the orbit. The main bacteria involved are *Streptococcus pneumoniae*, *Streptococcus pyogenes*, and *Staphylococcus aureus*. Trauma, dental infections, and bloodstream infections can also lead to orbital cellulitis. The infection triggers inflammation and swelling in the orbit, which can rapidly become dangerous without urgent treatment.
