Modern cytotoxic drugs increase the survival rate of children with Acute Lymphoblastic Leukaemia (ALL): But the eye is a pharmacological sanctuary and after clinical "cure" of the haematological disease the child may be blinded by leukaemic ocular infiltration. This is the history of a child who had had no recurrence of haematological leukaemia for four and a half years but following remission developed central nervous system (CNS) leukaemia followed by leukaemic iridocyclitis in the right eye after 20 months and in the left eye after three years three months from the initial diagnosis of ALL. Prophylactic cranial irradiation is performed on initial haematological diagnosis of ALL. This includes prophylactic irradiation of the posterior segment of the eye and optic nerve. Should this prophylactic irradiation of the posterior segment of the eye and optic nerve be repeated on diagnosis of CNS leukaemia and at specified intervals thereafter with recurrence of CNS leukaemia?