Benign orbital inflammatory disease

Dacryoadenitis forms just one class of orbital inflammation, but any orbital tissue may become inflamed either due to a specific aetiology or without a known cause. Scleritis and episcleritis are other subgroups of orbital inflammation that are discussed elsewhere.

Thyroid orbitopathy is a very specific form of orbital inflammation and is presented in Chapter 11.

Infective orbital cellulitis

Bacterial orbital infections are common and the age of the patient and site of origin help to indicate the likely organism and guide the selection of antibiotic therapy.

Preseptal infections generally arise from infected chalazia or insect bites and the eye remains uninflamed, with no chemosis, no proptosis and normal movements. Treatment is with an appropriate systemic antibiotic for soft-tissue cellulitis - such as a broad-spectrum cephalosporin - and review; drainage of a meibomian abscess will aid rapid resolution.

True orbital cellulitis (post-septal infection) presents with fever, systemic illness, periorbital swelling with proptosis, a red eye with chemosis and restricted eye movements (Figure 12.13). Optic neuropathy is present in more severe cases, being a sign of rising intraorbital pressure, and the onset of meningism or central neurological signs may herald the very serious complication of cavernous sinus thrombosis. In many cases there will be a history of antecedent upper respiratory tract infection or, in adults, a history of chronic sinus disease or dental infection. The most commonly identified bacteria are Staphylococcus aureus, Streptococcus species and, in children, also Haemophilus influenzae.

True infective orbital cellulitis is an emergency and requires immediate intravenous

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Figure 12.13 Orbital cellulitis in a child with persistent fever after coryza.

antibiotics; these should be given on clinical suspicion alone and their administration should not, under any circumstances, be delayed whilst arranging imaging or other investigations. Appropriate antibiotics should be at suitable dosage and active against the common organisms: a typical adult might receive Cefuroxime 1-5g every 8 hours (the child receiving a reduced dosage), along with Metronidazole 500mg every 8 hours in patients over the age of about 15.

When intravenous antibiotics have been given, thin slice CT of the orbits and sinuses will be required to demonstrate the likely source of infection and whether there is a localised collection of pus in the orbit or subperiosteal spaces. Once the orbital infection is controlled, with stabilisation or improvement in orbital status, then the patient should be referred for urgent treatment of the underlying sinus disease by an otorhinolaryngologist.

Where there is failing vision due to rising orbital pressure, the loss of vision can progress rapidly and lead to permanent blindness; in these cases, urgent drainage of the orbit is required and should be undertaken as an emergency. The site for primary exploration is indicated by the direction of globe displacement and drainage of pus and oedema (using, if urgency dictates, just local skin-infiltration anaesthesia) should be undertaken in the same fashion as drainage of an acute, sight-threatening haematoma (Chapter 14). When the focus of infection has been identified and drained, a corrugated drain should be left in place until there has been a clear improvement in orbital function.

If infective orbital cellulitis persists (or worsens after initial improvement) then the possibility of abscess formation, the presence of foreign material, reinfection with other bacteria, unusual organisms (fungi or tuberculosis) or a non-infective inflammatory cause (such as tumour necrosis) should be considered.

Severe complications of visual loss, cavernous sinus thrombosis and intracranial spread of infection may be secondary to late presentation, or progression due to inappropriate antibiotic selection at inadequate dosage; the latter situation should be preventable in most cases by close clinical monitoring.

Late abscess formation may require drainage to hasten resolution.

Orbital myositis

Typically presenting with a relatively sudden onset of orbital ache (worse on eye movement), ocular redness and diplopia, this condition is commonest in young women. The characteristic history and clinical signs -with pain worse when looking away from the field of action of the affected eye muscle - is sufficient to justify treatment with a non-steroidal anti-inflammatory drug, this typically relieving pain within a day. CT scan will demonstrate diffuse enlargement of one, or rarely more, eye muscles and, if severe, some "spillover" inflammatory changes in the surrounding orbital tissues.

Biopsy should be undertaken if the condition does not settle, with a view to treatment with systemic steroids or low-dose, lens-sparing irradiation of the retrobulbar tissues.

Patients may get recurrent episodes of myositis in various muscles and, in some cases, severe fibrosis of the affected muscles can result in a gross ocular deviation (Figure 12.14).

Idiopathic orbital inflammation

Idiopathic orbital inflammation occurs most commonly in the fourth and fifth decades, with no sex predilection, and is characterised by a polymorphous lymphoid infiltrate with a variable degree of fibrosis. It may present as an acute form with marked inflammation, or as a chronic form with a tendency to pain and fibrosis.

Figure 12.14 Restricted adduction and narrowing of the right palpebral aperture during adduction, due to fibrosis of the right lateral rectus after chronic myositis: (a) right gaze, (b) left gaze.

If inflammation is centred near the superior orbital fissure, a severe retrobulbar ache occurs with optic neuropathy, profound ophthalmoplegia and periorbital sensory loss, with almost no proptosis and relatively few inflammatory signs (Figure 12.15). This disease has a characteristically rapid and good response to high-dose systemic steroids, with resolution of pain and orbital signs within 24-48 hours.

CT scanning will demonstrate the extent of orbital involvement by the inflammation, with ill-defined opacity through the orbital fat and loss of definition of orbital structures. It is not, however, diagnostic and therefore biopsy is mandatory in all cases, except those with a characteristic history and response to treatment - namely orbital myositis and superior orbital fissure syndrome. The differential diagnoses for idiopathic orbital inflammation is extensive and includes infective orbital cellulitis, granulomatous orbital diseases (such as sarcoidosis or Wegener's granuloma), metastatic tumours and haematological malignancies, and appropriate systemic investigations (and biopsy) should be performed before starting systemic therapy.

Open biopsy at anterior orbitotomy will give the highest diagnostic yield and the

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