Non-arteritic Anterior Ischemic Optic Neuropathy (NAION) is a condition that affects the optic nerve, leading to sudden vision loss in one eye. It occurs when blood flow to the optic nerve is reduced, often due to small vessel disease. Risk factors include hypertension, diabetes, and sleep apnea. Symptoms typically include a sudden decrease in vision, often noticed upon waking. Unlike other forms of optic neuropathy, NAION is not caused by inflammation or arteritis. Diagnosis is usually made through a comprehensive eye examination and medical history, while treatment options are limited and focus on managing underlying conditions.