Preseptal Cellulitis

Axial contrast-enhanced CT image of the orbit shows soft tissue thickening of the right preseptal region (between arrows). The retroorbital fat is normal (arrowheads).

Facts:

• 'Periorbital' or 'preseptal' infection = infection of tissues anterior to orbital septum.
• Orbital septum separates preseptal space from orbit. Orbital septum is a connective tissue extension of periosteum reflected into upper and lower eyelids. It serves as a barrier to spread of infection to the orbit.
• Most common cause of preseptal cellulitis is localized infection of eyelid or adjacent structures (mostly due to S. aureus)
  

References:
1. Wald ER. Periorbital and orbital infections. Infect Dis Clin N Am 2007;21:393.
2. Lui I, et al. Preseptal and orbital cellulitis: a 10-year review of hospitalized patients. J Chin Med Assoc 2006;69:415.