Retrobulbar optic neuritis (RON) is a condition that affects the optic nerve, which is the bundle of nerve fibers that carries visual information from the eye to the brain. The optic nerve is located behind the eye, which is why the condition is referred to as "retrobulbar." RON is typically characterized by inflammation of the optic nerve, which can lead to a loss of vision. The exact cause of RON is not well understood, but it is thought to be an immune-mediated disorder. This means that the body's immune system mistakenly attacks the optic nerve, causing inflammation and damage. RON is often associated with other autoimmune disorders, such as multiple sclerosis (MS), but it can also occur on its own. Symptoms of RON typically include a sudden loss of vision in one eye, which may be accompanied by eye pain or tenderness. Other symptoms can include double vision, blurry vision, and sensitivity to light. The loss of vision caused by RON is often described as a "graying out" or "fading" of vision, rather than complete blindness. Diagnosis of RON is typically made based on a person's symptoms and a thorough eye examination. An eye doctor may perform tests such as visual acuity testing, visual field testing, and optical coherence tomography (OCT) to assess the health of the optic nerve and determine if there is any inflammation or damage. Blood tests may also be performed to check for other autoimmune disorders that may be associated with RON. Treatment for RON typically involves the use of corticosteroids to reduce inflammation and prevent further damage to the optic nerve. High-dose intravenous methylprednisolone (IVMP) is considered as the first-line treatment. Oral steroids may also be used. In addition to steroids, other medications may be used to manage symptoms and prevent complications. In most cases, the vision loss caused by RON is permanent, but the condition is usually not progressive, meaning it doesn't continue to get worse over time. However, in some cases, RON can lead to further vision loss or even blindness. Additionally, RON is a significant risk factor for developing multiple sclerosis, with about 50% of people who have RON developing MS within 10 years. In conclusion, Retrobulbar optic neuritis (RON) is a condition that affects the optic nerve, which is the bundle of nerve fibers that carries visual information from the eye to the brain. It is typically characterized by inflammation of the optic nerve, which can lead to a loss of vision. The exact cause of RON is not well understood, but it is thought to be an immune-mediated disorder. Symptoms of RON typically include a sudden loss of vision in one eye, which may be accompanied by eye pain or tenderness. Treatment for RON typically involves the use of corticosteroids to reduce inflammation and prevent further damage to the optic nerve. In most cases, the vision loss caused by RON is permanent but the condition is usually not progressive. However, RON is a significant risk factor for developing multiple sclerosis, with about 50% of people who have RON developing MS within 10 years. Dr. A. Arrazaghi. MD,FRCPC