Table 1. The International classification of retinoblastoma.

Group	Philadelphia version	Los Angeles version
A	Rb ≤3 mm	Rb ≤3 mm, at least 3 mm from the foveola, and 1.5 mm from optic nerve. No seeding
B	Rb>3 mm or  Macular location or  Juxtapapillary location (<1.5 mm to disc) or  SRF present	Eyes with no vitreous or subretinal seeding and retinal tumours of any size or location not included in group A. Small cuff of subretinal fluid ≤5 mm from tumour margin
C	Rb with  SRS ≤3 mm from Rb or  VS ≤3 mm from Rb	Eyes with focal vitreous or subretinal seeding and discrete tumour of any size or location. Seeding must be local, fine, and limited so as to be theoretically treatable with a radioactive plaque. Up to one quadrant subretinal fluid may be present.
D	Rb with  SRS >3 mm from Rb or  VS >3 mm from Rb	Eyes with diffuse vitreous or subretinal seeding and/or massive, nondiscrete endophytic or exophytic disease. Seeding more extensive than group C. Retinal detachment >1 quadrant
E	Rb with  Size >50% of globe or  Neovascular glaucoma or  Opaque media or  Invasion of optic nerve, choroid, sclera, orbit, anterior chamber	Massive Rb with anatomic or functional destruction of the eye with one or more of the following  Neovascular glaucoma  Massive intraocular haemorrhage  Aseptic orbital cellulitis  Tumour anterior to anterior vitreous face  Tumour touching lens  Diffuse infiltrating tumour  Phthisis or pre-phthisis

Abbreviations: Rb, retinoblastoma; SRF, subretinal fluid; SRS, subretinal seeds; VS, vitreous seeds.