Which of the following is NOT a known risk factor for NAION?

• A. Hypertension
• B. Diabetes mellitus
• C. Giant Cell Arteritis
• D. Hyperlipidemia

Answer: (C)

Non-arteritic ischemic optic neuropathy happens when the optic nerve head is poorly perfused, and vascular risk factors heighten that risk. Hypertension, diabetes mellitus, and hyperlipidemia are all linked to vascular disease and contribute to reduced ocular blood flow, making them established risk factors for NAION. Giant Cell Arteritis, in contrast, causes arteritic AION through inflammatory occlusion of the arteries supplying the optic nerve. It’s a different, inflammatory process, not a risk factor for the non-arteritic form. So the option that does not fit as a NAION risk factor is Giant Cell Arteritis.