eye disorders
Preseptal and Orbital Cellulitis
Etiology of Preseptal and Orbital Cellulitis
 is usually caused by contiguous spread of infection from local facial or eyelid injuries, insect or animal bites, Chalazion , or Orbital cellulitisis most often caused by extension of infection from adjacent sinuses, especially the ethmoid sinus. Less commonly, orbital cellulitis is caused by direct infection accompanying local trauma (eg, insect or animal bite, penetrating eyelid injuries) or contiguous spread of infection from the face or teeth or by hematogenous spread. Pathogens vary by etiology and patient age.Streptococcus pneumoniaeis the most frequent pathogen associated with sinus infection, whereasStaphylococcus aureusandStreptococcus pyogenespredominate when infection arises from local trauma.Haemophilus influenzaetype b, once a common cause, is now less common because of widespread vaccination. Fungi are uncommon pathogens, causing orbital cellulitis in patients who have diabetes or in those who are immunosuppressed. Infection in children<9 years is typically with a single aerobic organism; with increasing age, particularly age>15 years, infection is more typically polymicrobial with mixed aerobic and anaerobic (Bacteroides,Peptostreptococcus) infections. 