Hematological diseases can lead to ocular manifestations in up to 90% of patients and sometimes the ophthalmological findings are the presenting symptom of the disease. The ocular manifestation is often asymptomatic. The diagnosis can be difficult especially when the ocular manifestation represents the first symptoms. In most cases the conjunctiva and retina are involved and are particularly found in patients with anemia, leukemia, Hodgkin and non-Hodgkin lymphoma, myeloproliferative and myelodysplastic syndromes and coagulopathies. Even opportunistic infections in cases of hematological diseases can lead to ocular manifestations. For unexplained retinal alterations with hemorrhage and cotton-wool spots an underlying hematological disease should be excluded.