A 35-year-old woman presents with subacute visual loss in the right eye, periocular pain on eye movement, and a relative afferent pupillary defect (RAPD). MRI shows enhancement of the right optic nerve. The most likely diagnosis is:
- A Retrobulbar optic neuritis associated with multiple sclerosis ✓
- B Non-arteritic anterior ischaemic optic neuropathy
- C Leber's hereditary optic neuropathy
- D Papilloedema from raised intracranial pressure
Correct answer: A. Retrobulbar optic neuritis associated with multiple sclerosis
Explanation
Retrobulbar optic neuritis presents in young adults (20-45 years) with subacute monocular visual loss, pain on eye movement (due to inflammation of the optic nerve sheath where extraocular muscles attach), and a relative afferent pupillary defect (RAPD/Marcus Gunn pupil). The optic disc may appear normal initially (retrobulbar variety) but MRI with fat suppression shows gadolinium enhancement of the optic nerve. It is the presenting feature of MS in approximately 25% of cases; the Optic Neuritis Treatment Trial (ONTT) data supports IV methylprednisolone to hasten recovery.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.