Ophthalmology · Infectious Disease
The facts most likely to be tested
Periorbital cellulitis is an infection of the eyelid and surrounding skin anterior to the orbital septum.
The most critical clinical distinction is that extraocular movements (EOMs) are full and painless in preseptal cellulitis.
Patients with preseptal cellulitis lack proptosis, ophthalmoplegia, and pain with eye movement, which are hallmark signs of orbital cellulitis.
The most common pathogens in children are Staphylococcus aureus, Streptococcus species, and Haemophilus influenzae (in unvaccinated populations).
Computed tomography (CT) of the orbits with contrast is the diagnostic study of choice if the diagnosis is unclear or to rule out orbital involvement.
Physical examination reveals unilateral eyelid erythema, edema, and tenderness without signs of deep orbital space involvement.
Treatment involves systemic antibiotics (e.g., clindamycin or trimethoprim-sulfamethoxazole plus amoxicillin) with close outpatient follow-up for mild cases.
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A 5-year-old boy is brought to the urgent care clinic by his mother due to a 2-day history of swelling and redness of the left eyelid. The mother reports the child had a recent insect bite near the eye. On physical examination, the child has significant left eyelid edema and erythema, but the conjunctiva is clear. Extraocular movements are full and painless, and visual acuity is intact. There is no evidence of proptosis or afferent pupillary defect.
What is the most likely diagnosis?
Periorbital (preseptal) cellulitis
The presence of full, painless extraocular movements and the absence of proptosis or ophthalmoplegia distinguish preseptal cellulitis from the more serious orbital cellulitis.
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Etiology / Epidemiology
Common in children; usually secondary to sinusitis or skin trauma.
Clinical Manifestations
Unilateral eyelid erythema/edema; no ophthalmoplegia or pain with eye movement.
Diagnosis
CT scan of orbits with contrast is the gold standard to rule out orbital involvement.
Treatment
Empiric oral Amoxicillin-clavulanate; monitor for progression to orbital cellulitis.
Prognosis
Excellent prognosis with prompt treatment; 100% recovery if caught early.
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Epidemiology & Etiology
Most common in children <5 years old due to proximity to the ethmoid sinuses. Often follows impetigo, insect bites, or minor eyelid trauma. Primary pathogens include *Staphylococcus aureus* and *Streptococcus* species.
Pertinent Anatomy
The orbital septum acts as a fibrous barrier separating the superficial eyelid tissues from the deep orbital contents. Preseptal cellulitis is restricted to the anterior portion of this barrier.
Pathophysiology
Infection typically spreads from adjacent structures like the sinuses or via direct inoculation from skin breaks. Because the orbital septum remains intact, the infection is contained anteriorly. This prevents the development of deep orbital signs like proptosis or restricted motility.
Clinical Manifestations
Patients present with unilateral eyelid swelling, warmth, and erythema. Crucially, visual acuity and pupillary response remain normal. Pain with extraocular movement, proptosis, and ophthalmoplegia are absent; their presence suggests orbital cellulitis.
Diagnosis
Clinical diagnosis is often sufficient in mild cases. If the patient is toxic, uncooperative, or if orbital cellulitis is suspected, a CT scan of orbits with contrast is the gold standard. Look for preseptal soft tissue swelling without deep fat stranding.
Treatment
Outpatient management with oral Amoxicillin-clavulanate is standard for mild cases. If the patient is <1 year old or systemic signs are present, admit for IV antibiotics. Do not delay imaging if orbital involvement is suspected, as this is a vision-threatening emergency.
Prognosis
Most cases resolve rapidly with appropriate antibiotics. Orbital cellulitis is the primary complication, which can lead to cavernous sinus thrombosis or blindness. Close follow-up within 24-48 hours is mandatory.
Differential Diagnosis
Orbital Cellulitis: presence of ophthalmoplegia and pain with eye movement
Allergic reaction: bilateral involvement and intense pruritus
Contact dermatitis: history of exposure and lack of systemic symptoms
Dacryocystitis: inflammation localized to the medial canthus/lacrimal sac
Cavernous sinus thrombosis: bilateral signs and cranial nerve palsies