periorbital (“preseptal”) cellulitis is superficial and does not extend deep to the orbital septum but may do so in which case it becomes orbital cellulitis
orbital cellulitis extends deep to the orbital septum and risks permanent eye damage, intracranial infection and sepsis
infection is generally either local spread from soft tissues or sinuses, but may be systemically spread with seeding from bacteraemia / septicaemia eg. H. influenzae type b (HiB)
HiB vaccination of children since the early 1990s has practically eradicated life-threatening childhood invasive HiB infection such as orbital cellulitis, meningitis, septicaemia and epiglottitis
usual pathogens are Staph. aureus, Strept, H. influenzae type b (HiB), anaerobes, and in immunocompromised or diabetics, fungi may be the cause
orbital cellulitis is a rare emergency with risk of septic shock, intracranial spread (brain abscess or meningitis) and ocular damage and thus needs to be explicitly differentiated from periorbital cellulitis
features suggestive of orbital cellulitis rather than just periorbital cellulitis include:
children aged under 4yrs are at particular risk, especially if not vaccinated for H. influenzae type b (HiB)
immunocompromised patients
systemically unwell
fever
chemosis
proptosis
diplopia
painful eye movements
impaired visual acuity or visual fields
presence of a more likely aetiology such as:
orbital trauma
post-op
foreign body in orbit
NB. examination of the eye may be very difficult due to extreme swelling but should be pursued or CT scan performed if examination cannot exclude orbital cellulitis
NB. both periorbital and orbital cellulitis may be due to odontogenic sinusitis, dacrocystitis, or local infection but patients with periorbital cellulitis alone tend to be afebrile without eye signs or fever
necrotising fasciitis of the face is extremely rare
here is a case: necrotising fasciitis from an otherwise innocuous minor cut 1)
Mx of periorbital cellulitis in adults
those who are at low risk for HiB infection without concurrent sinusitis are generally covered for Staph. aureus
those with sinusitis or at risk of HiB are generally Rx with broad spectrum antibiotics - see your local guidelines
patients should be reviewed in 24hrs for response to Rx and exclusion of signs of orbital cellulitis
Mx of orbital cellulitis
blood cultures
usual bloods
if septic, start IV antibiotics ASAP (preferably within 1 hr)
eg. ceftriaxone + flucloxacillin (use vancomycin instead if MRSA risk) - see your local guidelines