Neurological examination - Eyes

🚨 Red flags: dysphagia, unplanned weight loss, anorexia, haematemesis/melaena, older age, lack of therapy response, chronic symptoms, long-term drug use.

👁️ Basics

• Know retinal anatomy & physiology – cones 🎨 (central, colour) vs rods 🌙 (peripheral, low light).
• Optic nerve exits nasal side; macula packed with cones.
• Optic pathways – essential to draw for exams 📝.
• Brainstem & CN III, IV, VI → control of eye movements.

👀 External Appearance

• 👁️‍🗨️ Partial Ptosis: Horner’s, myasthenia, dystrophy.
• ⬇️ Full Ptosis: CN III palsy.
• ⬆️ Lid Retraction: Graves’ eye disease.
• 👀 Proptosis: Graves’, orbital tumours, carotid–cavernous fistula, cellulitis.
• 🔴 Red Eye: Conjunctivitis, acute glaucoma, cellulitis, orbital mass.
• ↘️ Enophthalmos: Horner’s syndrome.

🌗 Pupils – Light Reflex

• Bright light → optic nerve → Edinger–Westphal nucleus → bilateral constriction via CN III.
• Check for RAPD (Marcus Gunn pupil 🔦).
• Pathology: Argyll Robertson pupil (accommodates but no light reaction).

📏 Pupils – Accommodation

• Look at distant point → then near (10 cm) → constriction + adduction expected.
• Controlled by frontal lobes, same efferent as light reflex.

🔵 Dilated Pupil

• 💊 Cocaine, adrenaline, anticholinergics.
• CN III palsy with headache → think SAH/PCOMM aneurysm 🚨.
• Holmes–Adie pupil: young women, slow constriction, ↓ reflexes.

⚫ Small Pupil

• Opiates, senile miosis, Horner’s, Argyll Robertson.
• Argyll Robertson pupils: irregular, no light reflex but accommodate → neurosyphilis, diabetes, midbrain tumour.

🐎 Horner’s Syndrome

• Triad: miosis + ptosis + anhidrosis (± enophthalmos).
• Light reflex intact.
• Causes:
  • Central: stroke, MS, syrinx.
  • Peripheral: Pancoast tumour, carotid dissection, trauma, aortic aneurysm.

📊 Visual Acuity

• Test each eye separately with Snellen chart (record 6/x).
• If no chart → newsprint at 30 cm. Use pinhole if no glasses.

⬇️ Causes of Reduced Acuity

• Cornea (ulcer, oedema), cataract, vitreous haemorrhage.
• Retina (infarct, haemorrhage).
• Optic neuropathy (MS, ischaemia, compression).
• Pathway lesions (stroke, occipital tumour).

🔥 Optic Neuritis

• Loss of vision + painful eye movements + colour desaturation.
• Common in MS. Disc swelling may be seen.

⚪ Optic Atrophy

• Pale disc, ↓ acuity, impaired colour vision.
• Causes: glaucoma, MS, ischaemic neuropathy, trauma, chronic papilloedema, Leber’s hereditary neuropathy.

🔦 RAPD (Relative Afferent Pupillary Defect)

• Swinging torch: affected eye dilates despite light → Marcus Gunn pupil.

👓 Visual Fields

• Screen quadrants by finger movements.
• Left field → right cortex, and vice versa.

📌 Common Visual Field Defects

• 🎯 Tunnel vision → glaucoma, retinitis pigmentosa, papilloedema.
• 🚫 Blind eye → optic nerve/eye pathology.
• ⏸️ Bitemporal hemianopia → pituitary/chiasm lesion.
• ➡️ Homonymous hemianopia → post-chiasmal (stroke, tumour).

🪞 Fundoscopy

• Dark lesions → melanoma, retinitis pigmentosa.
• Macula → cherry-red spot (CRA occlusion).
• Haemorrhages → dot/blot/flame 🔴.
• Optic disc → papilloedema, atrophy, glaucoma cupping.

👁️ Eye Movements

• Pursuit: Smooth following in “H” pattern.
• Saccades: Rapid switching between targets.

🔢 Cranial Nerves III, IV, VI

• CN III (Oculomotor): All except LR + SO → lesion = ptosis, “down & out”, dilated pupil.
• CN IV (Trochlear): SO → lesion = vertical diplopia.
• CN VI (Abducens): LR → lesion = cannot abduct, horizontal diplopia.

⚡ Internuclear Ophthalmoplegia (INO)

• MLF lesion → impaired horizontal gaze coordination.
• Classically in MS, also pontine infarct, diabetes.