Orbital cellulitis may be classified according to the microbial family of the offending pathogen (bacterial vs. fungal), or by the management protocol (medical vs. surgical therapy). In 1970, Chandler’s classification was created to describe five groups of orbital complications of sinusitis. This system is often used to describe the extent of orbital and periorbital disease.^[1]

Orbital cellulitis may be classified as follows:

• Bacterial vs. non-bacterial infection: This classification determines the course of the disease and the type of antibiotics to be used.
• Abscess vs. no abscess: This classification determines the need for surgical therapy.
• Chandler’s Classification of Orbital Complications of Sinusitis:^[1]
  • Stage I: Preseptal Cellulitis – Also known as periorbital cellulitis; this condition is not classified as true orbital cellulitis. It rarely extends to become true postseptal orbital cellulitis. It is characterized by lid edema, lack of proptosis, changes in visual acuity, pain with ocular movements, and opthalmoplegia.
  • Stage II: Orbital cellulitis – Also known as postseptal cellulitis or true orbital cellulitis; diffuse orbital inflammation without abscess formation.
  • Stage III: Subperiosteal abscess
  • Stage IV: Orbital abscess
  • Stage V: Intracranial involvement / cavernous sinus thrombosis