The prognosis (predicted outlook for survival) of eye cancer depends on the cancer’s stage, or how widespread it is in the body. A staging system devised by the Collaborative Ocular Melanoma Study group is probably the most widely used staging system for intraocular melanomas. This system categorizes melanomas by their size:

Another staging system for cancer is the TNM system, which was developed by the American Joint Committee on Cancer (AJCC):

• “T” describes the size of the tumor.
  
  
• “N” describes whether the cancer has spread to surrounding lymph nodes (bean-sized groups of immune system cells that help ward off infections and cancers).
  
  
• “M” describes whether or not the cancer has spread or metastasized to distant organs.

Information about the T, N and M categories is combined by a process called stage grouping to assign a stage to the eye cancer. The stages are labeled in order of severity, using Roman numerals and the letters “A” and “B.”

The five–year survival rate for small eye melanomas that are detected and treated early (in stage I or II) exceeds 90 percent. For larger eye melanomas, the rate is about 60 percent. Approximately half of patients with stage IV eye melanoma die within a year.

There is no unique system used to stage intraocular lymphomas.  However, this type of cancer may be staged using the system for non-Hodgkin’s lymphoma.

Physicians use the Reese-Ellsworth Staging System to stage retinoblastoma. This staging system is divided into five groups. The higher the group number, the less likely the patient will maintain vision.

The ganglion cells of the retina become the optic nerve at the optic disk. Because physicians cannot directly measure retinoblastomas, they compare the tumor’s size with the size of the optic disk, which is typically about 1/16 inch (1.5 mm). For instance, a tumor estimated to be four times the size of the optic disk (4 DD or 4 disk diameters) would be approximately 4/16 inch (6 mm) in diameter. The front and back halves of the eyeball are divided by an imaginary line called the equator.

The staging system for retinoblastoma is as follows:

• Group 1 (vision maintenance is very favorable):
  
  
• One or more tumors, smaller than 4 DD, all behind or at the equator
  
  
• Group 2 (vision maintenance is favorable):
  
  
• One or more tumors, between 4 DD and 10 DD, all behind or at the equator
  
  
• Group 3 (vision maintenance is doubtful):
  
  
• Any tumor located in front of the equator
  
  
• A single tumor, larger than 10 DD, located behind the equator
  
  
• Group 4 (vision maintenance is unfavorable):
  
  
• Multiple tumors, some exceeding 10 DD
  
  
• Any tumor that extends toward the ora serrata (the retina’s front edge)
  
  
• Group 4 (vision maintenance is very unfavorable):
  
  
• Tumors affecting over half the retina
  
  
• Vitreous seeding (the spread of tumors into the vitreous (the gel that fills the interior of the eye)

To simplify the staging process, physicians sometimes use the ABC Classification system: