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Tests and diagnosis

By Mayo Clinic staff

You're likely to see an ophthalmologist for a definitive diagnosis. The ophthalmologist may perform the following eye tests:

• A routine eye exam. Your eye doctor will check your vision and your ability to perceive different colors.
• Ophthalmoscopy. During this examination, your doctor shines a bright light into your eye and examines the structures at the back of your eye. This eye test evaluates the optic disk, which is the area where the optic nerve enters the retina in your eye. The optic disk becomes swollen in about one-third of people with optic neuritis.
• Pupillary light reaction test. Your doctor may move a flashlight in front of your eyes to see how your pupils respond when they're exposed to bright light. Pupils in eyes affected by optic neuritis don't constrict as much as those in healthy eyes do when stimulated by light.

Other tests to diagnose optic neuritis may include:

• Visual response test (Visual evoked potentials test). To perform this test, you sit before a screen on which an alternating checkerboard pattern is displayed. Attached to your head are wires with small patches to record your brain's responses to the visual stimuli. This type of test is able to detect the slowing of electrical conduction resulting from damaged areas on the optic nerve.
• Magnetic resonance imaging (MRI) scan. An MRI scan is a test that uses a magnetic field and pulses of radio wave energy to make pictures of your body. During an MRI to check for optic neuritis, you may be injected with a contrast solution to make the optic nerve and other parts of your brain more visible on the pictures. An MRI is also important to determine whether there are areas in your brain where the myelin has been damaged (lesions), which indicate a high risk of developing multiple sclerosis. An MRI also can help rule out tumors or other conditions that can mimic optic neuritis.
• Blood tests. A blood test is available to check for antibodies for neuromyelitis optica. People with severe optic neuritis may undergo this test to determine whether they're likely to develop neuromyelitis optica. An erythrocyte sedimentation rate (ESR) blood test is used to detect inflammation occurring in your body. This test may help determine whether optic neuritis is caused by inflamed cranial arteries (cranial arteritis).

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