Table 1.

International Intraocular Retinoblastoma Classification (IIRC)

Group A (very low-risk)	Small (<3mm) Discrete tumor at least 3 mm from foveola and 1.5 mm from optic nerve
GROUP B (low-risk)	Eyes with no vitreous or subretinal seeding and discrete retinal tumor of any size and location
GROUP C (moderate risk)	Eyes with only focal vitreous or subretinal seeding and discrete retinal tumor of any size and location. Minimal subretinal fluid (<1 quadrant)
GROUP D (high-risk)	Eyes with diffuse subretinal vitreous or subretinal seeding and/or massive non-discrete endophytic or exophytic disease. Eyes with more extensive seeding than Group C. Massive and/or diffuse intraocular disseminated disease may consist of fine or greasy vitreous seeding or avascular masses. Subretinal seeding may be plaque like. Included exophytic disease and more than one quadrant of retinal detachment
GROUP E (very high-risk)	Tumor touching the lens. Tumor anterior to anterior vitreous face. Diffuse infiltrating retinoblastoma. Irreversible neovascular glaucoma. Massive intraocular hemorrhage. Aseptic orbital cellulitis. Tumor necrosis. Phthisis bulbi or pre-phthisis

Notes: Reproduced from Fabian ID, Reddy A, Sagoo MS. Classification and staging of retinoblastoma. Community Eye Health. 2018;31(101):11-13.⁸