NeurologyTier 1Disease (DEADMAN)

Ophthalmological conditions - optic neuritis

Description

Inflammatory demyelination of the optic nerve -> subacute unilateral visual loss with pain on eye movement
Classic presentation of multiple sclerosis but also occurs in NMOSD, MOGAD, and idiopathically

F>M (~3:1), typical age 20-45
~50% of MS patients experience optic neuritis at some point; it is the presenting feature of MS in ~20%
~50% risk of developing MS within 15 years after a single episode of optic neuritis, higher with abnormal brain MRI at presentation

By underlying disease

Multiple sclerosis - commonest association in typical demographic (young, unilateral, retrobulbar)
NMOSD (neuromyelitis optica spectrum disorder) - aquaporin-4 antibody; more severe, often bilateral or with longitudinally extensive transverse myelitis
MOGAD (MOG antibody disease) - often bilateral, disc swelling more prominent, tends to relapse but usually better visual recovery than NMOSD
Idiopathic (isolated, no other disease identified)
Rare: post-infectious, sarcoidosis, syphilis, vitamin B12 deficiency (mimics)

Clinical

Subacute unilateral visual loss over hours-days, worsening over ~1-2 weeks
Pain with eye movement (~90%) - key discriminator from other causes of visual loss
Reduced colour vision (red desaturation) out of proportion to acuity loss
Relative afferent pupillary defect (RAPD)
Fundoscopy - normal disc in retrobulbar neuritis ("patient sees nothing, doctor sees nothing"), or disc swelling if anterior (more typical of MOGAD/children)

Investigations

MRI brain and orbits with gadolinium - the single most important test: enhancing optic nerve confirms diagnosis; brain lesion burden predicts MS conversion risk
Aquaporin-4 and MOG antibody serology - especially if bilateral, severe, poor recovery, or atypical for typical MS-associated optic neuritis
Visual evoked potentials - delayed latency, supportive but not required if MRI clear
Consider B12, syphilis serology, ACE/CXR (sarcoid) if atypical features

A. Acute

High-dose IV methylprednisolone (e.g. 1g/day for 3 days) - speeds visual recovery but does not change final visual outcome or long-term MS conversion risk
Oral corticosteroid alone (without preceding IV) is avoided - associated with increased relapse rate in the original ONTT trial
NMOSD/MOGAD-associated - more aggressive acute treatment often used (high-dose steroids +/- plasma exchange for severe/steroid-unresponsive visual loss) given worse visual prognosis

B. Disease-modifying therapy decision

MRI brain lesion burden at presentation guides MS risk discussion and disease-modifying therapy initiation - see Multiple sclerosis note for agent selection
NMOSD: long-term immunosuppression (rituximab, eculizumab, satralizumab per current evidence) - critical, as NMOSD relapses are frequently severe and cumulative
MOGAD: immunosuppression considered particularly if relapsing course

C. Supportive

Typical (MS-associated) optic neuritis - good visual recovery in most, often near-baseline by 6-12 months even without treatment changing the endpoint
NMOSD-associated optic neuritis has a much worse visual prognosis - higher risk of permanent severe visual loss, often bilateral
Residual subtle deficits common even after "recovery" - reduced contrast sensitivity, colour vision, Uhthoff phenomenon (transient worsening with heat/exercise)
Recurrence risk depends on underlying disease (higher and more damaging in NMOSD/MOGAD than typical MS-associated optic neuritis)

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