The incidence of choroidal invasion in retinoblastoma, and its effects on prognosis were investigated by studying serial sections of enucleated eyes. Each patient was observed for a minimum of five years. It was found that choroidal invasion is both more common and less dangerous than previously believed.
Redler LD, Ellsworth RM. Prognostic Importance of Choroidal Invasion in Retinoblastoma. Arch Ophthalmol. 1973;90(4):294-296. doi:10.1001/archopht.1973.01000050296009