Neurology · MU Sofia

11. Optic nerve: anatomy, physiology, examination, syndromes

Covers the anatomy of the optic nerve and its role in vision and the pupillary light reflex, with the visual pathway shown in pictures and the crossing of nasal retinal fibers at the chiasm highlighted. Walks through bedside examination: acuity, confrontation fields, colour vision, pupillary responses and fundoscopy. Then describes optic neuritis, optic atrophy and papilledema, and ends with visual field defects such as monocular blindness, hemianopias, quadrantanopias and scotomas, with their lesion sites.

Inside: 1 section · 3 labelled pictures · 15 flashcards · 2 min

Topic 11 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 338 words (2 min of reading), with 15 flashcards.

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  1. Optic never - anatomy, physiology, examination, syndromes

Optic never - anatomy, physiology, examination, syndromes

Anatomy: The optic nerve (CN II) is a sensory cranial nerve responsible for vision.

Visual Pathway

Important Rule: Nasal retinal fibers cross at the chiasm.. Temporal retinal fibers remain uncrossed.

Physiology

Functions: Vision. Visual acuity. Visual fields. Color vision. Afferent limb of the pupillary light reflex

Pupillary Light Reflex

Light → Retina → Optic nerve (CN II) → Midbrain → Oculomotor nerve (CN III) → Pupillary constriction

Examination of the Optic Nerve

  1. 1. Visual Acuity: Assessed using a Snellen chart (or near-vision chart).
  • Tests: Each eye separately. With corrective lenses if used
  1. 2. Visual Fields: Assessed by confrontation testing.
  • Examines: Peripheral vision. Detection of visual field defects.
  1. 3. Color Vision: Usually tested with Ishihara plates.
  • Useful in: Optic neuritis. Optic neuropathies
  1. 4. Pupillary Light Reflex
  • Evaluate: Direct response (illuminated eye constricts). Consensual response (opposite eye constricts). Tests integrity of CN II and CN III.
  1. 5. Fundoscopy (Ophthalmoscopy)
  • Examination of: Optic disc. Retina. Retinal vessels
  • Normal optic disc: Pink. Sharp margins

Optic Nerve Syndromes

  1. 1. Optic Neuritis: Inflammation of the optic nerve.
  • Features: Sudden visual loss. Pain on eye movement. Reduced color vision. Relative afferent pupillary defect (RAPD)
  • Common Cause: Multiple sclerosis
  1. 2. Optic Atrophy: Degeneration of optic nerve fibers.
  • Features: Progressive visual loss. Pale optic disc. Reduced visual acuity
  1. 3. Papilledema: Optic disc swelling due to increased intracranial pressure.
  • Features: Blurred vision. Headache. Nausea/vomiting. Bilateral swollen optic discs
  1. 4.Visual Field Defects
  • Monocular Blindness: Lesion in the Optic nerve
  • Finding: Complete loss of vision in one eye.
  • Bitemporal Hemianopia: Lesion at the Optic chiasm
  • Cause: Pituitary tumor (classic)
  • Finding: Loss of temporal visual fields in both eyes.
  • Homonymous Hemianopia: Lesion can be seen in ptic tract, optic radiation, or occipital cortex
  • Finding: Loss of the same visual field in both eyes.
  • Example: Right-sided lesion → Left homonymous hemianopia
  • Quadrantanopia: Temporal Lobe Lesion
  • Superior quadrantanopia ("Pie in the sky"): Parietal Lobe Lesion. Inferior quadrantanopia ("Pie on the floor")

Scotoma Definition: Localized area of decreased or absent vision surrounded by normal field. Types: Central scotoma. Paracentral scotoma. Arcuate scotoma( bow shaped)

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