Central retinal artery occlusion is typically a thromboembolic phenomenon associated with atherosclerotic disease. This case presentation describes a rare case of CRAO in a young male secondary to hyperviscosity syndrome as a first symptom ofMixed Phenotype Acute Leukaemia. It is imperative for emergency physicians to recognise an atypical presentation of painless vision loss and evaluate such patients thoroughly, ensuring timely and vision sparing interventions.