Which investigations should be performed to confirm a diagnosis of optic neuritis and rule out other conditions?

Investigations to confirm optic neuritis and exclude other conditions include:

• Clinical assessment: Detailed history and neurological examination to identify typical features such as painful vision loss and to exclude other neurological causes NICE NG220.
• Magnetic Resonance Imaging (MRI) of the brain and orbits: MRI is essential to confirm optic nerve inflammation and to exclude other causes such as compressive lesions or demyelinating plaques suggestive of multiple sclerosis NICE NG220.
• Visual function tests: Visual acuity, colour vision, and visual field testing help document the extent of visual impairment.
• Ophthalmological examination: Slit-lamp examination with dilated pupils to exclude uveitis or other ocular inflammatory conditions NICE CKS.
• Blood tests: To exclude infectious or inflammatory causes if clinically indicated, although not routinely required for typical optic neuritis NICE NG220.
• Referral to ophthalmology and neurology specialists: For further assessment and confirmation of diagnosis, including consideration of lumbar puncture or other investigations if atypical features are present NICE NG220.

These investigations help confirm optic neuritis and exclude other causes such as uveitis, glaucoma, or compressive optic neuropathies.