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Orbital cellulitis and preseptal cellulitis are the major infections of the ocular adnexal and orbital tissues. Orbital cellulitis is an infection of the soft tissues of the orbit posterior to the orbital septum. Preseptal cellulitis is an infection of the soft tissue of the eyelids and periocular region anterior to the orbital septum. Orbital cellulitis and preseptal cellulitis can sometimes be a continuum.
Orbital Cellulitis
Orbital cellulitis occurs in the following 3 situations:
- Extension of an infection from the paranasal sinuses or other periorbital structures such as the face, globe, or lacrimal sac.
- Direct inoculation of the orbit from trauma or surgery.
- Haematogenous spread from bacteraemia.
Bacterial Causes
Streptococcus species, Staphylococcus aureus, and Haemophilus influenza type B are the most common bacterial causes of orbital cellulitis.
Pseudomonas, Klebsiella, Eikenella, and Enterococcus are less common culprits.
Polymicrobial infections with aerobic and anaerobic bacteria are more common in patients aged 16 years or older.
Fungal Causes
Fungal causes of orbital cellulitis are most commonly Aspergillus and Mucor species.
Fungi can enter the orbit. Orbital cellulitis, because of fungal infections, carries a high mortality rate in patients who are immunosuppressed.
Preseptal Cellulitis
- Preseptal cellulitis may be caused by bacteria, viruses, fungi, or helminths.
- Upper respiratory tract infections, especially paranasal sinusitis, commonly precede orbital cellulitis and some cases of preseptal cellulitis.
- In 2 large case series, nearly two-thirds of cases of cellulitis were associated with upper respiratory tract infection. One half of these cases were from sinusitis.
- The most common organisms are Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus species, and anaerobes, reflecting the organisms that commonly cause upper respiratory tract infections and external eyelid infections.
- Blood and skin culture results are negative.
Choice of antibiotics:
A combination of broad-spectrum antibiotics covering for both gram positive and gram-negative organisms is required for preseptal cellulitis with the addition of anaerobic cover for orbital cellulitis.
- 3rd generation cephalosporin (ceftriaxone or cefotaxime) covers both gram positive and gram-negative organisms +/- Flucloxacillin to ensure adequate treatment of Staphylococcus aureus
- Metronidazole is used in orbital cellulitis to cover for anaerobic bacteria.
- Using Co-amoxiclav as monotherapy on cessation of intravenous therapy is useful.
- The use of Clindamycin is recommended in the presence of infections that involve the bone with osteomyelitis or those individuals who are allergic to cephalosporins and penicillins.
- Empiric therapy with Vancomycin is the preferred first-line agent in case of methicillin resistant.
Choice of anti-fungal:
Amphotericin is the antifungal medication of choice in the treatment of fungal orbital cellulitis. It is administered intravenously and, in cases of severe infection, may be appropriately provided before laboratory confirmation of fungal infection.
Decongestants:
Nasal decongestants like phenylephrine and Xylometazoline may help to open the sinus ostia and aid with drainage in cases of orbital cellulitis secondary to sinusitis.
Anti-Glaucoma:
Acetazolamide can lower the intraocular pressure in orbital cellulitis.
Corticosteroids:
Prednisone and prednisolone have anti-inflammatory properties and cause profound and varied metabolic effects.
Corticosteroids may be helpful, but they should not be started until after any surgery is performed and until the patient has been on appropriate antibiotics for 2-3 days.
References
1. Geoffrey M Kwitko,Geoffrey M Kwitko. Preseptal Cellulitis. http://emedicine.medscape.com/article/1218009-overview
2. John N Harrington. Orbital Cellulitis. http://emedicine.medscape.com/article/1217858-overview
3. Patrick Watts. Preseptal and orbital cellulitis in children.Paediatrics and Child Health 2016; 26 (1), http://www.sciencedirect.com/science/article/pii/S1751722215002231.
