Periorbital Cellulitis and Preseptal Cellulitis Are the Same Condition
Periorbital cellulitis and preseptal cellulitis are synonymous terms referring to the identical clinical entity—an infection confined to the eyelid and soft tissues anterior to the orbital septum. 1
Terminology Clarification
Both terms describe infection limited to tissues in front of the orbital septum, without involvement of the orbital contents (globe, extraocular muscles, or retrobulbar fat). 1
The terms are used interchangeably in clinical practice and medical literature, though "preseptal cellulitis" has become the preferred nomenclature in recent guidelines. 2, 3
The critical distinction is not between "periorbital" versus "preseptal," but rather between preseptal cellulitis (anterior to the septum) and orbital cellulitis (posterior to the septum). 4, 5
Key Anatomic Landmark: The Orbital Septum
The orbital septum is a thin fibrous membrane extending from the periosteum of the orbital rim to the tarsal plates of the eyelids, serving as the anatomic boundary that separates preseptal from orbital infections. 6
Infections anterior to this septum remain confined to the eyelid and surrounding skin, while infections posterior to it involve the orbital contents and carry risk of vision loss and intracranial complications. 4, 6
Clinical Features of Preseptal (Periorbital) Cellulitis
Diffuse periorbital erythema and edema without clear borders, warmth across the affected eyelid and periorbital tissues, and tenderness throughout the swollen area. 2
Crucially, preseptal cellulitis demonstrates normal extraocular movements, no proptosis, and preserved vision—these findings distinguish it from orbital cellulitis. 2, 3
Eyelid swelling may be substantial but the globe itself is not involved. 5, 7
Pathogenesis Varies by Patient Age and Mechanism
In infants and young children, preseptal cellulitis often results from bacteremia (typically Haemophilus influenzae type b or Streptococcus pneumoniae) without other apparent focus. 8
In older children and adults, preseptal cellulitis usually arises from localized trauma or disruption of skin integrity, most commonly caused by Staphylococcus aureus or Streptococcus pyogenes. 1, 8
A subset of periorbital swelling associated with paranasal sinusitis represents inflammatory edema from venous obstruction rather than true soft tissue infection, though this is still classified under the preseptal cellulitis umbrella. 8
Critical Distinction: Preseptal vs. Orbital Cellulitis
Proptosis, impaired or painful extraocular movements, decreased visual acuity, and ophthalmoplegia are red flags indicating orbital (postseptal) involvement requiring immediate hospitalization and IV antibiotics. 3, 4
Diplopia and movement restriction occur only with orbital cellulitis, never with isolated preseptal disease. 7
Fever is present in 51.5% of preseptal cases versus 82.2% of orbital cases, and C-reactive protein is significantly higher in orbital cellulitis (median 136 mg/L vs. 18 mg/L). 7
Imaging Decisions
Preseptal cellulitis is diagnosed clinically without imaging when examination reliably excludes orbital involvement. 2, 3
CT orbits with IV contrast should be obtained if any clinical findings suggest orbital involvement, if the eyelid is more than 50% closed preventing adequate examination, or if no improvement occurs after 24-48 hours of antibiotics. 3, 4
CT accurately differentiates preseptal from postseptal disease and identifies complications such as subperiosteal abscess, orbital abscess, or cavernous sinus thrombosis. 4
Common Pitfall to Avoid
Assuming all periorbital swelling is benign preseptal cellulitis can delay diagnosis of orbital cellulitis, which requires urgent intervention to prevent permanent vision loss, cavernous sinus thrombosis, or death. 2, 4
Always assess for proptosis (comparing to the contralateral eye), extraocular movements in all directions (pain with movement indicates postseptal involvement), visual acuity, and pupillary response before labeling a case as simple preseptal cellulitis. 3, 4