This paper reports minimally visible tumour recurrence that was detectable on spectral domain OCT (SD-OCT) in a two-month old infant who had a diagnosis of bilateral familial retinoblastoma. The infant was treated with IVC for six cycles with vincristine, etoposide and carboplatin. All scar areas in each eye were treated with transpupillary thermotherapy or cryotherapy. At one month follow-up, there was a stable clinical appearance and no evidence of recurrence on ophthalmoscopy or ultrasound. However, hand-held SD-OCT revealed recurrence which, on second look ophthalmoscopy, confirmed a barely visible transparent recurrence requiring cutting cryotherapy. At 12-month follow-up, no recurrence was detected. The authors recommend intraoperative SD-OCT as a non-invasive, effective assessment of retinoblastoma treatment response and for documenting tumour location, response, foveal anatomy and prediction of ultimate potential visual outcome.