Explaining the difference between preseptal and orbital cellulitis — OSCE

Candidate instructions (8-minute station)

You are the paediatric registrar in the emergency department. A 3-year-old child has a one-day history of left eyelid swelling and redness after an insect bite. The child is afebrile and well, the eye is white and quiet, eye movements are full and painless, and the vision is normal. The parent is anxious and wants to know whether the eye is infected, whether the child needs to go to hospital, and what to watch for. [3]

Your tasks are: [3]

1. Explain the diagnosis of preseptal cellulitis in plain language and reassure the parent that the eye itself is safe. [3]
2. Explain why the child does not need a scan or admission, and outline the oral antibiotic treatment and review plan. [3]
3. Give a clear, specific safety-net for the signs that would mean the infection has crossed into the orbit and needs an urgent return. [1]
4. Explain the importance of completing the course and keeping the area clean. [9]

You are not expected to prescribe intravenous antibiotics or to arrange imaging for this child, because the examination confirms there are no orbital signs. [9]

Examiner prompt to the actor (parent)

"It looks so angry and swollen — is the eyeball itself infected? Will she lose her sight? Does she need antibiotics through a drip or a scan? I am so worried I barely slept." [3]

Marking domains

• Frame and reassurance (3): explains preseptal cellulitis as a skin infection of the eyelid in front of a protective barrier called the orbital septum, not an infection of the eyeball itself; reassures that the septum is intact, the eye is safe and the child is well, so sight is not at risk; names that it is common and very treatable. [3]
• Treatment and the no-scan, no-admission reasoning (3): explains that because the eye moves normally, there is no bulging and the vision is fine, the child does not need a scan or a drip and can take oral antibiotics at home — co-amoxiclav or cephalexin for five to seven days — with a review in 24 to 48 hours to confirm improvement. [3] [9]
• Safety-net for orbital signs (2): tells the parent to return urgently if the eye starts to bulge forward, if the child cannot move the eye normally or it hurts to look around, if the vision changes or the child complains of blurred vision, or if the child becomes febrile and unwell — because those signs would mean the infection has crossed behind the barrier into the orbit and would need admission, a scan and intravenous antibiotics. [1]
• Course completion and hygiene (2): emphasises completing the full antibiotic course even when the swelling settles, keeping the area clean with gentle washing, avoiding rubbing, and hand hygiene to prevent spread — because stopping early risks recurrence and the portal of entry from the insect bite needs to heal. [9]

Model answer — the explanatory script

"Thank you for bringing her in. I can see why the swelling looks frightening, but I have examined her carefully and I have good news — the eyeball itself is not infected, her sight is safe, and this is a common problem that we can treat at home." [3]

"What she has is called preseptal cellulitis — it is an infection of the skin and soft tissues of the eyelid, the same as any skin infection, which started where the insect bit her. The reason her sight is safe is that there is a tough barrier called the orbital septum that sits between the eyelid and the eyeball, and I have checked very carefully that this barrier is intact. Her eye moves in every direction without pain, it is not bulging, and her vision is perfect. So the infection is in front of the barrier, not behind it, and that makes all the difference." [3]

"Because the barrier is intact and she is well, she does not need a scan and she does not need antibiotics through a drip. She can take an antibiotic syrup by mouth at home — co-amoxiclav or cephalexin, twice a day for five to seven days. I would like to see her again in one to two days to make sure the swelling is settling, and most children improve quickly." [3] [9]

"Now, the most important thing I want you to watch for is whether the infection crosses behind that barrier into the orbit. If that happened, it would be a different and more serious problem. So please bring her straight back if her eye starts to bulge forward, if she cannot move the eye normally or it hurts when she tries to look around, if she tells you her vision has changed or is blurry, or if she becomes hot and unwell with a fever. Any of those would mean the infection has moved behind the barrier and we would need to admit her, do a scan and give antibiotics through a drip. Those signs are not common with what she has, but they are the ones that matter, and I would rather you brought her back to be checked than waited." [1]

"Finally, please finish the whole course of the antibiotic syrup even when the swelling looks better — stopping early can let the infection come back. Keep the area clean with gentle washing, discourage her from rubbing or scratching, and wash her hands often. The bite that let the infection in needs to heal, and keeping it clean is what helps that happen. If the swelling has not started to improve in 48 hours, or sooner if any of those warning signs appear, please come straight back." [9]