**4. Most common predisposing factors for orbital cellulitis**

In the most reported series, the most common predisposing factor for orbital cellulitis is sinus disease, especially in children. [1], [4], [8] Usually, the infection originates from sinusitis. It can originate from face or eyelids after a recent or past trauma, dental abscess or from a distant source by hematogenous spread. [1], [8], [11-13] For simplification purposes, Chandler et al, [6] grouped complication of sinus inflammation into 5 classes. In the group 1, eyelids may be swollen alongwith presence of orbital content edema (preseptal cellulitis). Swelling may reflect impedance of drainage through ethmoidal vessels. Group II reflects evidence of orbital cellulitis in which inflammatory cells diffusely infiltrate orbital tissues. In Group II, the eyelids may be swollen along with conjunctival chemosis as well as some degree of proptosis. Visual loss may be present in Group II patients. Purulent material may be collecting as subperiosteal abscess between the periorbita and the bony walls of the orbit in Group III. These patients may have significant conjunctival chemosis, eyelid edema, along with tenderness in the involved areas with variable degree of proptosis, and decreased ocular motility. The abscess may be anywhere in the vicinity of the orbit. Patients in group IV (orbital abscess), may present with their abscess being inside or outside the muscle cone following untreated orbital cellulitis. These patients may have significantly more pain, proptosis, decreased ocular motility and variable degree of severe visual loss. Patients in group V may present with bilateral eyelid edema along with involvement of third, fifth and sixth cranial nerves which is thought to be due to the extension of the infectious process into the cavernous sinus with formation of thrombosis. These patients may have nausea, vomiting along with signs of nervous system involvement which could also be due to septicemia. Signs of proptosis, eyelid edema, optic neuritis, frozen globe, decreased supra-orbital nerve conduction may be hallmarks of orbital apex syndrome which is thought to be due to the sinusitis in the area of the superior orbital fissure and optic foramen. [14]

**Figure 3.** External photographs of a young male child who suffered trauma over his right brow area after which he developed orbital cellulitis and formation of an abscess that required drainage.

Our own experience in treating orbital cellulitis from a developing country confirmed previous observations from the Western countries in which sinusitis has been implicated as the cause of orbital cellulitis in most of the cases. [8] Specifically in children, vast majority of cases with orbital cellulitis had pre-existing sinusitis, and significant number of them had multiple sinuses involved. Our experience revealed that unlike patients from the Western countries, most patients with sinusitis and orbital cellulitis in the developing countries had sought treatment later in the course of their disease. Unlike Western countries, in our patients, prior history of periocular trauma or ocular/ periocular surgery were also very common cause of orbital cellulitis. (Figure 3). [1], [10] Although less common, dacryocystitis, dental infection and endophthalmitis, were also found to be the cause of orbital cellulitis in our patients (Figure 4). [8] Patients with prior history of sinusitis may also develop osteomyelitis and intracranial infection. In these cases, osteomyelitis, commonly involve the frontal bone which is due to a direct extension of frontal infection or septic thrombophlebitis via the valveless sinus of Breschet. [15] Less common cause of osteomyelitis results from the ethmoidal sinusitis because from this location, infection can rapidly spread through the thin lamina papyracea into the orbit or maxilla, where arterial anastomoses are sufficient to prevent necrosis due to septic thrombosis of a single artery. Although meningitis may be the most common intracranial complication of sinus disease, epidural, subdural and brain parenchymal abscess can also develop. [15]

**Figure 4.** External photograph and U/S of right eye of an 83-years-old male who suffered right eye trauma and then developed panophthalmitis resulting in total loss of his vision.
