This case report describes the unilateral acute reduction of vision in the right eye of a 48-year-old woman. The patient was otherwise healthy but 2 days previously had suffered from dizziness and blurred vision. Secondary to this, the patient had already been under dental treatment for 1 week due to gingival swelling. At the first examination a macular branch retinal vein occlusion and Roth spots were found in the right eye by indirect ophthalmoscopy. The immediate diagnostic procedure identified aute amyeloid leukemia (AML) as the cause of the vascular pathology. The AML can be manifested in different ways and the retina is involved in approximately 50% of cases. Due to a secondary hyperviscosity syndrome, which is found in approx. 20% of acute leukaemias, symptomatic central vein occlusion or macular branch vein occlusion can occur. Ophthalmic symptoms can be the first and only signs to be detected. Therefore, ophthalmologists should also consider a systemic disease and initiate a clarification. A differential blood count is indispensable. The results usually improve by a rapidly arranged and suitable therapy. Ophthalmological follow-up examinations are imperative as an initiated chemotherapy can also produce ophthalmological side-effects.