Which of the following is typically found in a patient with optic neuritis but NOT NAION?

• A. Unilateral vision loss
• B. APD
• C. Color vision defects
• D. Pain on eye movement

Answer: (D)

Pain with eye movement is a hallmark of optic neuritis because the inflammation that demyelizes the optic nerve irritates the nerve and its surrounding sheath. When the eye moves, the inflamed nerve is stretched and the irritated fibers generate pain, often described as a retrobulbar ache that can worsen with movement. Non-arteritic anterior ischemic optic neuropathy, on the other hand, is caused by vascular ischemia to the optic nerve and typically presents as a sudden, painless loss of vision. While other signs like unilateral vision loss, an afferent pupillary defect, or color vision changes can occur in either condition, the presence of pain with eye movement most strongly points toward optic neuritis.