16 Oct 2026 · Case #041
Orbital cellulitis
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Diagnosis
Orbital cellulitis
First-line treatment
IV antibiotics with surgical drainage
How the diagnosis is reached
Every red swollen eyelid forces the same question, and the answer decides between an oral antibiotic at home and an emergency admission: is the infection in front of the orbital septum or behind it. Preseptal cellulitis stops at the lid. The eye moves fully and painlessly, acuity is normal, the pupil reacts normally and the globe sits where it should. This boy has the opposite of all four. Pain on movement, restricted movement with diplopia, a globe pushed forwards, and reduced acuity are the findings that place the infection behind the septum, and any one of them mandates imaging. The route in is anatomical. The ethmoid sinuses sit directly medial to the orbit, separated only by the lamina papyracea, a plate of bone thin enough to be named for paper, so a week of ethmoid sinusitis in a child is the commonest origin of exactly this. What raises the urgency further is the optic nerve. A relative afferent pupillary defect with desaturated colour vision and falling acuity means the nerve is being compressed by the collection, and colour vision usually fails before acuity does, which is why the plates are worth doing. Untreated, infection here spreads backwards through valveless orbital veins into the cavernous sinus, or intracranially, and blindness can follow within a day. Admission and intravenous broad-spectrum antibiotics start at once, covering staphylococci, streptococci and the anaerobes that come with a sinus source, and given intravenously rather than orally because the orbit is a closed compartment that oral therapy penetrates poorly. Drainage is not optional here: there is a rim-enhancing collection, and the failing acuity, desaturated colour vision and afferent pupillary defect say the nerve is already being compressed. Vision and eye movements are then rechecked every few hours through the first day, with imaging repeated if anything worsens.
Key clinical clues
- A week of sinus congestion preceding the swollen lid, pointing to an ethmoid source
- Pain on eye movement with diplopia, which never happens in preseptal cellulitis
- A globe pushed forwards and displaced away from the affected sinus wall
- A relative afferent pupillary defect with desaturated colour vision and reduced acuity
- A rim-enhancing collection along the medial orbital wall on CT
The case in full
Presenting complaint
Patient history
A 12-year-old boy is brought in with two days of increasing swelling and redness around the right eye. He has had a heavy cold with nasal congestion for the past week.
Change since this morning
Symptoms
The eye has become painful to move and he says he sees double when he looks to the side. His mother thinks the eye itself now looks as though it is bulging forwards.
Examination and observations
Physical examination
The right lid is tense, red and swollen, and opens only with difficulty. The globe is pushed forwards and slightly down and out. Eye movements are restricted and painful in every direction. The left eye is entirely normal.
| Parameter | Value | Reference |
|---|---|---|
| Temperature | 38.9 °CRef 36.1–37.5 | 36.1–37.5 |
| Heart rate | 112 bpmRef 60–100 | 60–100 |
| Blood pressure | 108/66 mmHg | – |
| Respiratory rate | 20 /minRef 12–20 | 12–20 |
Formal eye assessment
Physical examination
The affected eye is assessed properly at the slit lamp and with bedside tests.
| Parameter | Value | Reference |
|---|---|---|
| Visual acuity, right | 6/12Ref 6/6 | 6/6 |
| Visual acuity, left | 6/6Ref 6/6 | 6/6 |
| Colour plates, right | 9 of 17Ref 17 of 17 | 17 of 17 |
| Relative afferent pupillary defect | Present on the rightRef Absent | Absent |
| Intraocular pressure, right | 24 mmHgRef 10–21 | 10–21 |
Blood tests
Laboratory results
Bloods and cultures are sent before antibiotics.
| Parameter | Value | Reference |
|---|---|---|
| White cell count | 19.2 ×10⁹/LRef 4.0–11.0 | 4.0–11.0 |
| Neutrophils | 16.4 ×10⁹/LRef 2.0–7.5 | 2.0–7.5 |
| CRP | 168 mg/LRef <5 | <5 |
| Blood cultures | Sent, pendingRef No growth | No growth |
Cross-sectional imaging
Imaging
Contrast-enhanced CT of the orbits and sinuses is obtained. The right ethmoid cells are opacified, and a rim-enhancing collection tracks through the thin medial orbital wall, pushing the medial rectus and the globe outwards. The other orbit is clear.