1. Orbit 2 Orbital infections Dr. Mohammad Shehadeh

2. Preseptal cellulitis Preseptal cellulitis is an infection of the subcutaneous tissues anterior to the orbital septum. Although not strictly an orbital disease, it is included here because it must be differentiated from the much less common but potentially more serious orbital cellulitis. Occasionally rapid progression to orbital cellulitis may occur

3. Causes 1.Skin trauma such as laceration or insect bites. The offending organism is usually S. aureus or S. pyogenes. 2.Spread of local infection, such as from an acute hordeolum, dacryocystitis or sinusitis. 3.From remote infection of the upper respiratory tract or middle ear by haematogenous spread.

4. Signs 1.Unilateral tender and red lid with periorbital oedema (Fig. 3.13A). 2.In contrast to orbital cellulitis proptosis and chemosis are absent; visual acuity, pupillary reactions and ocular motility are unimpaired. CT shows opacification anterior to the orbital septum

5. Treatment is with oral co-amoxiclav 500/125 mg every 8 hours. Severe infection may require intravenous antibiotics.

7. Bacterial orbital cellulitis Bacterial orbital cellulitis is a life-threatening infection of the soft tissues behind the orbital septum. It can occur at any age but is more common in children. The most common causative organisms are S. pneumoniae, S. aureus, S. pyogenes and H. influenzae.

8. Pathogenesis 1.Sinus-related, most commonly ethmoidal, typically affects children and young adults. 2.Extension of preseptal cellulitis through the orbital septum. 3.Local spread from adjacent dacryocystitis, mid-facial or dental infection. 4.Haematogenous spread. 5.Post-traumatic develops within 72 hours of an injury that penetrates the orbital septum. 6.Post-surgical may complicate retinal, lacrimal or orbital surgery.

9. Presentation: is with the rapid onset of severe malaise, fever, pain and visual impairment. Signs 1.Unilateral tender warm and red periorbital and lid oedema. 2.Proptosis 3.Painful ophthalmoplegia (Fig. 3.14A). 4.Optic nerve dysfunction.

10. CT shows opacification posterior to the orbital septum (Fig. 3.14B).

12. Complications 1.Ocular complications include exposure keratopathy, raised intraocular pressure, occlusion of the central retinal artery or vein, endophthalmitis and optic neuropathy. 2.Intracranial complications, which are rare but extremely serious, include meningitis, brain abscess and cavernous sinus thrombosis. 3.Subperiosteal abscess is most frequently located along the medial orbital wall.

13. Treatment 1.Hospital admission with otolaryngological assessment and frequent ophthalmic review is mandatory. 2.Antibiotic therapy involves intravenous ceftazidime, with oral metronidazole to cover anaerobes. Vancomycin is a useful alternative in the context of penicillin allergy. Antibiotic therapy should be continued until the patient has been apyrexial for 4 days. 3.Monitoring of optic nerve function every 4 hours by testing pupillary reactions, visual acuity, colour vision and light brightness appreciation.

14. Surgical intervention in which the infected sinuses and orbital collections are drained should be considered in the following circumstances: 1.Lack of response to antibiotics. 2.Subperiosteal or intracranial abscess. 3. Atypical picture, which may merit a biopsy.

15. Rhino-orbital mucormycosis Mucormycosis is a very rare opportunistic infection caused by fungi of the family Mucoraceae, which typically affects patients with diabetic ketoacidosis or immunosuppression This aggressive and often fatal infection