What condition is primarily indicated by the presence of optic neuritis?

The presence of optic neuritis is primarily associated with Multiple Sclerosis (MS). This condition involves inflammation of the optic nerve, which can result in symptoms such as vision loss, light sensitivity, and pain. Optic neuritis frequently occurs as a result of the demyelination that characterizes Multiple Sclerosis, where the immune system attacks the protective covering of nerves, leading to inflammation and impaired transmission of visual signals.

While other conditions listed, such as Alzheimer's Disease, Glaucoma, and Diabetic Retinopathy, can affect vision, they do not typically present with optic neuritis as a primary symptom. Alzheimer's Disease is primarily a neurodegenerative disorder affecting memory rather than direct optic nerve inflammation. Glaucoma involves intraocular pressure leading to damage to the optic nerve, but this differs from the inflammatory process found in optic neuritis. Diabetic Retinopathy is a condition resulting from damage to the retinal blood vessels due to diabetes but does not involve the optic nerve itself. Thus, the presence of optic neuritis is a significant indicator of Multiple Sclerosis, making it the correct answer.