Table 1

The Reese Ellworth classification

Group I
     a) solitary tumor, < 4 disc diameters in size, at or behind the equator
     b) multiple tumor, none > 4 disc diameters in size, at or behind the equator

Group II
     a) solitary tumor, 4–10 disc diameters in size, at or behind the equator
     b) multiple tumor, 4–10 disc diameters in size, behind the equator

Group III
     a) any lesion anterior to the equator
     b) solitary tumor >10 disc diameters behind the equator

Group IV
     a) multiple tumors, some >10 disk diameters
     b) any lesion extending anteriorly to the ora serrata

Group V
     a) massive tumors involving more than half the retina
     b) vitreous seeding

Aerts et al. Orphanet Journal of Rare Diseases 2006 1:31   doi:10.1186/1750-1172-1-31