About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Preseptal: eyelid swelling anterior to orbital septum — oral co-amoxiclav
- Orbital: infection behind the septum — proptosis, painful EOMs, ophthalmoplegia — EMERGENCY
- Most common cause: ethmoidal sinusitis spreading through lamina papyracea
- CT orbits with contrast identifies abscess
- Orbital: IV ceftriaxone + metronidazole; surgical drainage if RAPD or large abscess
Overview
Periorbital (preseptal) cellulitis is infection anterior to the orbital septum. Orbital (postseptal) cellulitis involves the orbital fat, muscles, and optic nerve behind the septum. Orbital cellulitis carries risks of visual loss, cavernous sinus thrombosis, intracranial abscess, and meningitis. Most commonly caused by direct spread from ethmoidal sinusitis.
Epidemiology
Periorbital is far more common, especially in children under 10. Orbital cellulitis incidence ~1.6 per 100,000 children per year, commonest age 5–10. More common in winter (sinusitis season). Common organisms: S. pneumoniae, S. pyogenes, S. aureus, H. influenzae.
Clinical Features
Symptoms
Eyelid swelling, redness, warmth
Fever
Painful eye movements (orbital)
Reduced or double vision (orbital)
Signs
Proptosis — hallmark of ORBITAL cellulitis
Ophthalmoplegia — restricted painful eye movements
Reduced VA or RAPD — optic nerve compromise
Full EOMs + normal vision + no proptosis = likely preseptal
Investigations
First-line
CT orbits with contrastESSENTIAL for orbital cellulitis — identifies abscess
Blood cultures, FBC, CRPBefore starting IV antibiotics
VA and pupil assessmentRAPD = optic nerve compromise = urgent surgery
Second-line
MRI orbits and brainIf intracranial extension suspected
Management
RCOphth and local Trust guidelines1
Preseptal cellulitis
- Oral co-amoxiclav 625 mg TDS for 7–10 days
- Safety net for orbital signs
- Review 24–48 hours
2
Orbital cellulitis — emergency
- IV ceftriaxone 2 g OD + metronidazole 500 mg TDS
- Joint: ophthalmology + ENT + microbiology
- Monitor VA/pupils/EOMs 4–6 hourly
- Surgical drainage if RAPD, deteriorating vision, or large abscess
Complications
- Subperiosteal/orbital abscess
- Vision loss
- Cavernous sinus thrombosis: Bilateral signs + cranial nerve palsies + sepsis
- Intracranial abscess or meningitis
UKMLA Exam Tips
- 1Preseptal vs orbital: proptosis + painful EOMs + reduced VA = ORBITAL
- 2Orbital cellulitis = emergency admission, IV antibiotics, CT orbits
- 3Ethmoidal sinusitis is the commonest cause — spreads through thin lamina papyracea
- 4RAPD = urgent surgical drainage
- 5Cavernous sinus thrombosis: bilateral orbital signs + CN palsies + sepsis
Put your reading into practice
Topic-specific question practice is not linked for this article yet.
Choose UKMLA questions from the existing bank. General exam practice covers your selected topics; it is not filtered to this article. Your usual question-bank access applies.
Choose UKMLA practiceAfter your session, return to this section to revisit the reading and choose your next review.
Verified Sources & References
related resources
Save your place and choose what comes next
Ophthalmology · Article 10 of 15