Posterior ischemic optic neuropathy (PION) is a condition that occurs when there is insufficient blood flow to the optic nerve, leading to vision loss. This can happen due to various factors, including low blood pressure, surgery, or conditions that affect blood circulation. PION typically affects the back part of the optic nerve, which is crucial for transmitting visual information from the eye to the brain. Symptoms of PION often include sudden vision loss in one or both eyes, which may be accompanied by a lack of pain. Diagnosis usually involves a comprehensive eye examination and imaging studies to assess the optic nerve. Treatment focuses on addressing the underlying causes to improve blood flow and prevent further damage.