MS PG Ophthalmology Theory Exam Questions

Topic: Ophthalmic Division of the Trigeminal Nerve (V1)

References: Kanski's Clinical Ophthalmology 10e, AK Khurana, Duke-Elder / Standard sources

LONG ANSWER QUESTION (10 Marks)

Model Answer

• Enters the superior orbital fissure outside the common tendinous ring (annulus of Zinn)
• Passes forward between the levator palpebrae superioris and the periorbita on the roof of the orbit
• Divides into two terminal branches:
  • Supraorbital nerve - exits through the supraorbital notch/foramen; supplies the upper eyelid, conjunctiva, forehead, and scalp as far back as the middle of the scalp
  • Supratrochlear nerve - exits medial to the supraorbital foramen; supplies the conjunctiva and skin of the upper eyelid and lower medial forehead

• Enters the superior orbital fissure outside the common tendinous ring
• Passes forward along the upper border of the lateral rectus muscle
• Receives a communicating branch from the zygomaticotemporal nerve (carrying postganglionic parasympathetic fibers from the pterygopalatine ganglion for secretomotor supply to the lacrimal gland)
• Supplies: lacrimal gland, conjunctiva, and the lateral part of the upper eyelid

• Enters the superior orbital fissure inside the common tendinous ring, along with the optic nerve and ophthalmic artery
• Crosses superior to the optic nerve passing medially, below the superior rectus
• Branches:
  • Sensory (communicating) root to ciliary ganglion - carries sensory fibers from the eyeball through the ganglion without synapsing
  • Long ciliary nerves (2-3) - sensory to the eyeball (cornea, iris, ciliary body); also carry sympathetic fibers for pupillary dilation (dilator pupillae)
  • Posterior ethmoidal nerve - exits through posterior ethmoidal foramen; supplies posterior ethmoidal air cells and sphenoidal sinus
  • Infratrochlear nerve - supplies medial upper and lower eyelids, lacrimal sac, conjunctiva, and skin of the upper half of the nose
  • Anterior ethmoidal nerve - exits through anterior ethmoidal foramen; supplies anterior cranial fossa, nasal cavity, and skin of the lower half/tip of the nose (external nasal nerve, the terminal branch)

• A parasympathetic ganglion located in the posterior orbit, lateral to the optic nerve, between it and the lateral rectus
• Three roots:
  • Parasympathetic root (motor/long root) - from inferior branch of CN III; preganglionic fibers synapse here; postganglionic fibers travel via short ciliary nerves to sphincter pupillae (miosis) and ciliary muscle (accommodation)
  • Sympathetic root - postganglionic fibers from superior cervical ganglion via carotid plexus; pass through without synapsing; supply dilator pupillae and blood vessels
  • Sensory root - from nasociliary nerve; passes through without synapsing; sensory from eyeball

• HZO results from reactivation of varicella-zoster virus (VZV) latent in the trigeminal ganglion, specifically along the ophthalmic division (V1)
• The rash is dermatomal, unilateral, does not cross the midline, and involves the upper eyelid/forehead
• Hutchinson's Sign: Vesicles on the tip and side of the nose indicate involvement of the external nasal branch of the anterior ethmoidal nerve (a terminal branch of the nasociliary nerve). This predicts a high risk of ocular involvement (keratitis, uveitis, scleritis), because the nasociliary nerve supplies the eye
• Ocular complications include: neurotrophic keratitis, corneal dendrites, uveitis, secondary glaucoma, optic neuritis, and cranial nerve palsies

"Ocular symptoms can occur after zoster eruption in any branch of the trigeminal nerve but are particularly common when vesicles form on the nose, reflecting nasociliary (V1) nerve involvement (Hutchinson's sign)." - Harrison's Principles of Internal Medicine 22e

SHORT ANSWER QUESTIONS (5 Marks each)

MCQ-STYLE VIVA QUESTIONS

• (A) Nasociliary nerve
• (B) Lacrimal nerve
• (C) Frontal nerve ✓
• (D) Infratrochlear nerve

• (A) Long ciliary nerve
• (B) Infratrochlear nerve
• (C) Posterior ethmoidal nerve
• (D) External nasal nerve (anterior ethmoidal nerve terminal branch) ✓

• (A) Outside the annulus of Zinn, with the frontal nerve
• (B) Inside the annulus of Zinn ✓
• (C) Through the optic canal
• (D) Outside the annulus, with the lacrimal nerve

• (A) Long ciliary nerve
• (B) Nasociliary nerve (V1) ✓
• (C) Lacrimal nerve
• (D) Supraorbital nerve

• (A) Frontal nerve
• (B) Lacrimal nerve
• (C) Nasociliary nerve ✓
• (D) Oculomotor nerve (CN III)

• (A) Nasociliary nerve (V1)
• (B) Greater petrosal nerve
• (C) Inferior division of oculomotor nerve (CN III) ✓
• (D) Facial nerve (CN VII)

KEY EXAM POINTS TO REMEMBER

1. V1 is purely sensory; it has no motor component
2. Three branches before entering orbit: Frontal (largest), Lacrimal (smallest), Nasociliary
3. Frontal and Lacrimal nerves enter the superior orbital fissure outside the annulus of Zinn
4. Nasociliary nerve enters inside the annulus of Zinn
5. The nasociliary nerve is the most clinically important branch - it is the afferent limb of the corneal reflex and carries sensory fibers from the eye
6. Ciliary ganglion has 3 roots: parasympathetic (from CN III - the only one that synapses here), sympathetic, and sensory (from nasociliary)
7. Hutchinson's sign = vesicles on tip/side of nose = nasociliary involvement = high risk of eye disease in HZO
8. Tolosa-Hunt syndrome = inflammation of superior orbital fissure/apex causing ophthalmoplegia + V1 anesthesia + pain
9. The supraorbital nerve is the terminal branch of the frontal nerve that supplies the forehead up to the vertex