Background: the orbital septum
The orbital septum is a fibrous sheet which is attached peripherally around the margin of the orbit where it is continuous with the periosteum. Centrally, it fuses into the tarsal plates. It effectively separates the eyelids from the contents of the orbital cavity.
Orbital cellulitis versus preseptal cellulitis
Orbital cellulitis is an extremely serious (potentially life-threatening) but uncommon ophthalmic emergency characterised by infection of the soft tissues behind the orbital septum. Preseptal cellulitis refers to the much more common and far less serious infection anterior to the orbital septum. Very occasionally, preseptal cellulitis progresses to orbital cellulitis; this is more likely in children. Orbital cellulitis and preseptal cellulitis are not terms that can be used interchangeably.
Orbital cellulitis: pathophysiology
This often arises in one of three situations:
- As an extension of an infection from the periorbital structures (usually the paranasal sinuses: ethmoid sinusitis is the most common causative factor, accounting for 90% of cases) and also from the face, the globe, the lacrimal sac and dental infection (via an intermediary maxillary sinusitis).
- As a result of direct inoculation of the orbit from trauma (accidental or surgical - including orbital, lacrimal, strabismus and vitreo-retinal surgery). Post-traumatic orbital cellulitis tends to develop within 72h of the injury.
- Due to haematogenous spread from distant bacteraemia.
Occasionally, it may occur as an extension of preseptal cellulitis, particularly in young children in whom the orbital septum is not fully developed. The pathogens most commonly involved are the aerobic, non spore-forming bacteria - Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes and Haemophilus influenzae (the latter classically found in children although there has been a significant decline in this organism over the past couple of decades). Mucormycosis associated with patients who have diabetic ketoacidosis or immunosuppression is also described. This very rare and rapidly spreading infection caused by fungi, is aggressive and often fatal. There has recently been an emergence of Methicillin-resistant S. aureus (MRSA) in the organisms isolated; this is rare but the development is worrying. Orbital cellulitis may be complicated by spread to adjacent structures and to the central nervous system.
Preseptal cellulitis: pathophysiology
This may also arise in one of three situations:
- As a result of local skin trauma such as lacerations and insect bites.
- Due to spread from local infection such as dacrocystitis, hordeolum and paranasal sinuses.
- Spread from distant infections such as those outlined above as well as from the upper respiratory tract.
The most common pathogenic organisms are S. aureus, S. epidermidis, streptococci and anaerobes. MRSA has also been isolated in cases but again, this currently remains very rare. In this day and age of bioterrorist threat, it is worth noting that both anthrax and smallpox cause preseptal cellulitis but clearly, in this situation, patients will present with a host of other problems. The orbital septum limits spread to associated structures and notably to the central nervous system.
- Orbital cellulitis is much less common than preseptal cellulitis although data relating to the exact incidence is scant.
- Both conditions occur more commonly in the winter months owing to the increased incidence of paranasal sinus infection.
- There is no predilection for gender or race (except in children where orbital cellulitis affects four times as many females).
- Both conditions are more common in children: orbital cellulitis more frequently affects 7-12 year olds whereas preseptal cellulitis occurs at younger ages (80% of patients are under 10 years of age and most are younger than 5 with a mean age of 21 months).
- Pre-septal and orbital cellulitis have both been described following eyebrow piercing.
|Additional notes||Eye itself may be slightly injected but is otherwise relatively uninvolved.||Other positive findings may include conjunctival chemosis and injection, a purulent discharge and evidence of endophthalmitis.|
- Orbital/preseptal cellulitis
- Necrotising fasciitis
- Allergic lid swelling
- Severe viral conjunctivitis
- Cavernous sinus thrombosis
- Other orbital conditions eg thyroid eye disease, orbital tumours/pseudotumours, orbital vasculitis
- Other conditions eg insect bite, angioedema, maxillary osteomyelitis
- Diagnosis is usually made based on the clinical findings and investigations are aimed at identifying the root cause of the infection - particularly in the case of orbital cellulitis. Investigations are carried out in the hospital setting.
- A full blood count frequently shows a leucocytosis (>15 X109) but blood cultures are frequently negative in adults. They cannot be counted on to differentiate between pre-septal and orbital cellulitis. In children < 7 or 8 years of age, S. pneumoniae and H. influenzae may be found.
- Any discharge from skin breaks should be swabbed and sent to microbiology. Throat swabs and samples of nasal secretions may also help diagnosis.
- CT of the sinuses as well as the orbit ± brain if intracranial abscess is suspected, remains the gold standard imaging modality, carried out to identify any subperiosteal abscesses, paranasal sinusitis or cavernous sinus thrombosis (all needing multi-speciality input). It is also valuable in assessing trauma cases where there may be concerns about a retained orbital or intraocular foreign body.
- An MRI may complement the CT in diagnosing a cavernous sinus thrombosis.
- If cerebral or meningeal signs develop, the patient may need a lumbar puncture.
Orbital infections fall into one of five categories:
- Stage I - preseptal cellulitis
- Stage II - orbital cellulitis
- Stage III - subperiosteal abscess (which may arise from orbital cellulitis or paranasal sinusitis)
- Stage IV - orbital abscess (a complication of orbital cellulitis)
- Stage V - cavernous sinus thrombosis and infection (the cavernous sinus drains venous blood from both eyes)
- Adults: 250(qds) - 500(tds)mg oral co-amoxiclav depending on severity of infection, for 10 days with daily review until there is definite improvement (then every 2-7 days until complete recovery).
- Children: 20-40mg/kg/day oral co-amoxiclav over 24h in three divided doses.
- Lid abscesses should be drained.
Clinical improvement should occur over 24-48 hours. Refer if patient is systemically unwell, if there is doubt over the diagnosis, if the patient is not responding to treatment or if drainage of a lid abscess is required. It is prudent to refer all children. Hospital management may involve intravenous therapy (1-2gm iv ceftriaxone daily until response is seen) and further investigation to confirm that this is indeed a simple preseptal cellulitis and that there are no unusual organisms involved. ENT will be involved if sinusitis is found.
- Hospital admission under the joint care of the ophthalmologists and the ENT surgeons is mandatory. (Prior to the advent of antibiotics, orbital cellulitis had a mortality rate of 17% and 20% of the survivors were blind in the affected eye.)
- These patients will have a full set of investigations (see above).
- Intramuscular - or more commonly - intravenous antibiotics are used (eg ceftriaxone 1-4gm daily with 1-2gm flucloxacillin qds) in addition to metronidazole in patients over 10 years old with chronic sinonasal disease.
- Clindamycin plus a quinolone such as ciprofloxacin are used where there is penicillin sensitivity. Vancomycin is also an alternative.
- Optic nerve function is monitored every 4 hours (pupillary reactions, visual acuity, colour vision and light brightness appreciation).
- Treatment may be modified according to microbiology results and lasts for 7-10 days.
- Surgery is indicated where there is CT evidence of an orbital collection, where there is no response to antibiotic treatment, where visual acuity decreases and where there is an atypical picture which may warrant a diagnostic biopsy. Surgery often concurrently warrants drainage of infected sinuses.
- Progression to stage II and beyond of orbital infections.
- Unusually, lagophthalmos, lid abscess, cicatricial ectropion and lid necrosis may also be seen in these patients.
- Ocular: exposure keratopathy (which can lead to visual loss through permanent damage to the cornea), raised intraocular pressure, central retinal artery or vein occlusion, endophthalmitis, optic neuropathy.
- Orbital abscess: more often associated with post-traumatic orbital cellulitis. Blindness can occur through direct extension of the infection to the optic nerve. About 11% of cases lose their vision.
- Subperiosteal abscess: usually located along the medial orbital wall. This may progress intracranially.
- Intracranial (rare): meningitis (~2%), brain abscess (~1%), cavernous sinus thrombosis (which itself can lead to spread to the brain or affect the pituitary gland). The latter is very rare in developed countries and is associated with a mortality rate of >50%.
Early recognition and appropriate treatment should carry a good prognosis, particularly in the absence of complications. However immunosuppressed individuals are more susceptible to complications and fungal cellulitis can be associated with a high rate of mortality.
Prophylactic antibiotics are prudent in the management of surgical and accidental trauma to the lid. Chloramphenicol ointment is a good first choice, applied qds to the clean wound for a week. Traumatic lid laceration also benefits from a review a 48-72h down the line to help identify any emerging preseptal cellulitis early.
There is no definitive preventative management other than the optimal treatment of any precipitative factors such as sinusitis.
Further reading & references
- Rimon A, Hoffer V, Prais D, et al; Periorbital cellulitis in the era of Haemophilus influenzae type B vaccine: predisposing factors and etiologic agents in hospitalized children. J Pediatr Ophthalmol Strabismus. 2008 Sep-Oct;45(5):300-4.
- Harrington JN; Cellulitis. eMedicine, December 2008.
- Denniston AKO, Murray PI. Oxford Handbook of Ophthalmology (OUP), 2009.
- Handbook of Ocular Disease Management; Orbital Cellulitis.
- Donahue SP, Schwartz G.; Preseptal and orbital cellulitis in childhood. A changing microbiologic spectrum. Ophthalmol, 1998;105(10):1902-5[abstract].
- Jackson TL; Moorfields Manual of Ophthalmology, Mosby (2008)
- Kanski J. Clinical Ophthalmology; A Systematic Approach (5th Ed) Butterworth Heinemann (2003)
- Witherspoon SR, Blomquist PH; Methicillin-resistant Staphylococcus. Ophthalmology. 2007 Jul;114(7):1420-1.
- Handbook of Ocular Disease Management; Preseptal Cellulitis.
- Sobol AL, Hutcheson KA; Cellulitis, Preseptal. eMedicine, April 2008.
- Sadovsky R; Distinguishing periorbital from orbital cellulitis. American Family Physician, March 2003.
- Carelli R, Fimiani F, Iovine A, et al; Ocular complications of eyebrow piercing. J Pediatr Ophthalmol Strabismus. 2008 May-Jun;45(3):184-5.
- Kunimoto DY, Kanitkar KD, Makar MS; The Wills Eye Manual (4th Ed), Lippincott, Williams and Wilkins (2004)
- British Society for Antimicrobial Chemotherapy (BSAC); Orbital cellulitis.
- Anand RV, Rajesh H, Kumar MA; Pre-septal cellulitis - Varied clinical presentations. Indian J Ophth, 1996;44(4):225-227.
|Original Author: Dr Olivia Scott||Current Version: Dr Olivia Scott|
|Last Checked: 17/09/2010||Document ID: 2543 Version: 22||© EMIS|
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