Can polycythemia (increased red blood cell count) cause anterior ischemic optic neuropathy (AION)?

From the Guidelines

Yes, polycythemia can cause anterior ischemic optic neuropathy (AION) due to increased blood viscosity leading to impaired blood flow to the optic nerve head, resulting in ischemia and damage to the optic nerve. Polycythemia, a condition characterized by an abnormally high concentration of red blood cells, increases blood viscosity which can impair blood flow to the optic nerve head. This reduced perfusion can lead to ischemia and subsequent damage to the optic nerve, resulting in AION. The mechanism involves hyperviscosity causing sluggish blood flow, microvascular occlusions, and thrombosis in the small vessels supplying the optic nerve.

Key Points to Consider

• Patients with polycythemia who develop visual symptoms should be evaluated promptly by an ophthalmologist.
• Management typically involves treating the underlying polycythemia through phlebotomy to reduce hematocrit levels to normal range (typically below 45%), hydration, and possibly cytoreductive therapy in cases of polycythemia vera, as recommended by the European LeukemiaNet 1.
• Aspirin therapy (81-100 mg daily) may also be recommended to reduce thrombotic risk, as shown in the European Collaboration on Low-Dose Aspirin in Polycythemia vera (ECLAP) study 1.
• Regular ophthalmologic monitoring is essential for patients with polycythemia to detect early signs of optic nerve compromise.
• The risk of thrombosis, including AION, is increased in patients with polycythemia, particularly those with a history of thrombotic events or cardiovascular risk factors, as noted in the study by the International Working Group on Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) 1.

Treatment and Management

• Phlebotomy to reduce hematocrit levels to normal range (typically below 45%) is the primary treatment for polycythemia, as recommended by the European LeukemiaNet 1.
• Cytoreductive therapy, such as hydroxyurea or interferon alfa-2, may be indicated in cases of polycythemia vera, particularly in high-risk patients or those with symptomatic or progressive splenomegaly, as noted in the study by the European Organisation for Research and Treatment of Cancer 1.
• Aspirin therapy (81-100 mg daily) may be recommended to reduce thrombotic risk, as shown in the ECLAP study 1.

From the Research

Association between Polycythemia and Anterior Ischemic Optic Neuropathy (AION)

• Polycythemia, a condition characterized by an increased red blood cell count, has been associated with AION in several case reports 2, 3.
• A case report published in 2008 described a 63-year-old woman with polycythemia vera who developed bilateral AION, suggesting a possible link between the two conditions 2.
• Another case report published in 2012 described a 56-year-old man with polycythemia vera who developed impending AION and retinal vein occlusion while being treated with interferon alpha 3.

Pathophysiology and Risk Factors

• The exact pathophysiology of AION is not fully understood, but it is thought to be related to ischemia of the optic nerve head 4.
• Risk factors for AION include age, hypertension, diabetes, and hypercholesterolemia 5, 6.
• Polycythemia may contribute to the development of AION by increasing blood viscosity and promoting thrombosis 2, 3.

Management and Treatment

• There is no established treatment for AION, but management of underlying risk factors and systemic diseases is essential 5, 6.
• In cases where polycythemia is suspected to be contributing to AION, treatment of the underlying condition may be necessary 2, 3.
• The use of aspirin and other antiplatelet agents may be considered for secondary prevention of AION, although the evidence is limited 6.