Optic Neuritis

Features

•    Painful monocular vision loss

•    Worse with eye movements

•    Decreased colour vision (red desaturation)

•    Relative afferent pupillary defect (RAPD)

•    Central scotoma common

Associations

•    Multiple sclerosis (most common)

•    Neuromyelitis optica (consider in severe, bilateral cases)

•    Viral infections (rare)

Prognosis

•    Spontaneous improvement within weeks in most cases

Optic Atrophy

Features

•    Pale optic disc on fundoscopy

•    Decreased visual acuity and contrast sensitivity

•    Visual field defects vary (central or peripheral)

Causes

•    Previous optic neuritis (MS)

•    Chronic glaucoma

•    Compressive lesions (e.g., tumours)

•    Ischaemic optic neuropathy

•    Toxic/nutritional (e.g., methanol, ethambutol, vitamin B12 deficiency)

Papilloedema

Features

•    Bilateral optic disc swelling due to increased intracranial pressure (ICP)

•    Preserved visual acuity early

•    Transient visual obscurations (seconds)

•    Enlarged blind spot

Causes

•    Mass lesions (tumour, abscess)

•    Idiopathic intracranial hypertension (IIH) — young obese women

•    Cerebral venous sinus thrombosis

•    Severe hypertension (hypertensive crisis)

Urgency

•    Requires urgent neuroimaging to exclude space-occupying lesion before LP

Anterior Ischaemic Optic Neuropathy (AION)

Features

•    Sudden painless monocular vision loss

•    Altitudinal (sectoral) visual field defect

•    Swollen pale optic disc

Causes

•    Arteritic: giant cell arteritis (GCA)

o    Scalp tenderness, jaw claudication, high ESR/CRP

•    Non-arteritic: small vessel disease (diabetes, hypertension)

Management

•    High-dose steroids immediately if GCA suspected

Visual Field Defects

Pattern                                Common Cause

Central scotoma                  Optic neuritis

Enlarged blind spot              Papilloedema

Altitudinal defect                   AION, branch retinal artery occlusion

Bitemporal hemianopia        Optic chiasm lesion (e.g., pituitary adenoma)

Homonymous hemianopia   Optic tract, occipital cortex

Quadrantanopia                    Temporal (superior) or parietal (inferior) lesions

Extra Revision Pearls

•    Painful monocular loss clue → optic neuritis; painless → AION, CRAO

•    RAPD clue → severe unilateral or asymmetric optic nerve disease

•    GCA clue → scalp tenderness, raised ESR, immediate steroids

•    Methanol clue → toxic optic atrophy with profound bilateral loss

•    Papilloedema clue → bilateral, transient blackouts on bending or straining

•    Central scotoma clue → optic nerve head or macular involvement