Orbital Cellulitis

What's going on?

This term is often used incorrectly. The orbit consists of the loose connective tissue that surrounds and cushions the globe. It is separated from the tissue lying just behind the upper and lower lids by a fibrous sheet called the orbital septum. Infection within the orbit is called true orbital cellulitis and is sight-threatening because of significant proptosis and optic nerve compromise.

If the infection involves only the skin of the lid anterior to the orbital septum, the condition is called preseptal cellulitis.

Preseptal cellulitis is of much less concern than true orbital cellulitis. Differentiating between the two is relatively straightforward, but it is always prudent to err on the side of caution when dealing with this condition.

Both orbital and preseptal cellulitis manifest as erythematous, swollen and cellulitic lids. The lids may be so swollen as to preclude a view of the eye itself. After opening the lids (you may have to prise them apart), if you find that the patient's eye is white, the pupils are reacting normally, ocular movements are full and the vision is unaffected, then the patient has preseptal cellulitis. If any of the above is impaired or the eye is frankly red, the patient is assumed to have orbital cellulitis.

Many patients affected by preseptal and orbital cellulitis are children.

Patients with true orbital cellulitis tend to be systemically unwell with pyrexia.

If I examine the patient, what will I find?

See above.

What if I've diagnosed it?

If the patient has mild preseptal cellulitis, a short trial of oral antibiotics may resolve it.

Always remember that preseptal cellulitis may rapidly progress to orbital cellulitis. If at any stage the eye itself becomes red, the patient should be assumed to have orbital cellulitis and referred urgently.

If the lids are so swollen as to preclude an adequate examination of the eye, then the patient should be assumed to have sight-threatening orbital cellulitis and referred urgently.

Children can progress rapidly to true sight-threatening orbital cellulitis, so it is wise to use a lower index for referral to a paediatrician, in order that a short course of intravenous antibiotics can be considered. In general, children under five years with preseptal cellulitis should be admitted for intravenous antibiotics.

What will the hospital do?

Practice varies. The ideal approach is multidisciplinary, with the patient being assessed by paediatricians and the ear, nose and throat and ophthalmology teams. Preseptal cellulitis may be managed by intravenous antibiotics and daily review to pick up early development of orbital cellulitis. In orbital cellulitis, CT imaging should be carried out urgently and further management decided upon this basis. If there is pus in the orbit (usually from sinus extension), then early surgical drainage is required.

What do I need to do?

The sinuses are often the source of any bacterial inoculum that enters the orbit. Once the event has resolved it is worth assessing the patient for indolent chronic sinusitis.

What to tell the patient

In preseptal cellulitis, the infection is localised to the lid, so the prognosis is good, although there is a significant risk of developing sight-threatening orbital cellulitis. Tell the patient that if their vision deteriorates or the eye itself becomes red, they should re-attend your surgery or hospital eye casualty immediately.

Problems that may arise, and how to deal with them

Chronic sinus disease should be addressed, as it may predispose to further orbital or preseptal infective episodes.