Neuro-Ophthalmology — MCQs

Neuro-Ophthalmology Indian Medical PG Practice Questions and MCQs

Question 171: Light reflex absent but accommodation reflex present is seen in?

A. Hutchison's pupil
B. Argyll Robertson pupil (Correct Answer)
C. Adie's pupil
D. Horner's syndrome

Explanation: **Explanation:** The clinical phenomenon where the **light reflex is absent but the accommodation reflex is preserved** is known as **Light-Near Dissociation (LND)**. **1. Why Argyll Robertson Pupil (ARP) is correct:** ARP is the classic example of LND. It is typically bilateral and characterized by small, irregular pupils that do not constrict to light but do constrict to accommodation. The lesion is believed to be in the **tectotegmental tract** (periaqueductal gray matter), which carries fibers from the pretectal nucleus to the Edinger-Westphal (EW) nucleus. The accommodation fibers, which approach the EW nucleus from a more ventral position, are spared, while the dorsal light reflex fibers are destroyed. It is a hallmark of **Neurosyphilis** (Tabes Dorsalis). **2. Why other options are incorrect:** * **Hutchinson's Pupil:** Seen in uncal herniation. It involves a fixed, dilated pupil due to compression of the 3rd cranial nerve; both light and accommodation reflexes are lost. * **Adie’s Tonic Pupil:** Characterized by a "slow" reaction. While it shows LND, the pupil is typically **dilated** (unilateral) and reacts very slowly to near stimuli, unlike the small, briskly accommodating pupil in ARP. * **Horner’s Syndrome:** Caused by sympathetic denervation. The pupil is miotic but reacts **normally** to both light and accommodation. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for ARP:** **A**ccommodation **R**etained, **P**upillary light reflex lost (**ARP**). Also, "Prostitute's Pupil" (accommodates but doesn't react). * **Site of Lesion:** Pretectal nucleus/Tectotegmental tract. * **Other causes of LND:** Diabetes Mellitus, Pinealoma (Parinaud Syndrome), and Myotonic Dystrophy. * **Reverse LND:** (Light reflex present, Accommodation absent) is seen in **Adie's pupil** (during recovery) or certain midbrain lesions.

Question 172: A patient with ptosis presents with retraction of the ptotic eyelid on chewing. What does this represent?

A. Marcus Gunn Jaw Winking syndrome (Correct Answer)
B. Third nerve misdirection syndrome
C. Abducent palsy
D. Oculomotor palsy

Explanation: ### Explanation **Correct Answer: A. Marcus Gunn Jaw Winking syndrome** **Underlying Concept:** Marcus Gunn Jaw Winking syndrome is a type of **congenital synkinetic ptosis**. It occurs due to a **pathological miswiring (aberrant innervation)** between the branches of two cranial nerves: the **Mandibular branch of the Trigeminal nerve (CN V3)**, which supplies the muscles of mastication, and the **Oculomotor nerve (CN III)**, which supplies the Levator Palpebrae Superioris (LPS). When the patient moves their jaw (chewing, sucking, or opening the mouth), the pterygoid muscles are activated, and due to the miswiring, the LPS also receives a signal, causing the ptotic eyelid to retract or "wink." **Analysis of Incorrect Options:** * **B. Third nerve misdirection syndrome:** This is an *acquired* synkinesis (often post-trauma or recovery from CN III palsy). It typically presents as "Pseudo-Graefe sign," where the eyelid retracts during **adduction or downward gaze**, not during jaw movements. * **C & D. Abducent (VI) and Oculomotor (III) palsy:** These present with ophthalmoplegia (restricted eye movements) and/or ptosis, but they do not involve synkinetic eyelid retraction triggered by the jaw. **High-Yield Clinical Pearls for NEET-PG:** * **Most common** type of congenital neurogenic ptosis (accounts for ~5% of cases). * **Inverse Marcus Gunn Phenomenon (Marin-Amat Syndrome):** The eyelid *closes* (ptosis worsens) upon jaw opening. This is usually acquired after facial nerve palsy. * **Marcus Gunn Pupil:** This is a separate entity (Relative Afferent Pupillary Defect - RAPD) and should not be confused with the Jaw Winking syndrome. * **Management:** If severe, the treatment of choice is **LPS excision (levator denervation) followed by a Frontalis Sling operation.**

Question 173: Which cranial nerve supplies the superior oblique muscle?

A. Oculomotor nerve (CN III)
B. Trochlear nerve (CN IV) (Correct Answer)
C. Trigeminal nerve (CN V)
D. Abducens nerve (CN VI)

Explanation: The innervation of the extraocular muscles is a high-yield topic in neuro-ophthalmology, easily remembered by the mnemonic formula: **LR6 (SO4) 3**. ### 1. Why the Correct Answer is Right The **Trochlear nerve (CN IV)** supplies the **Superior Oblique (SO)** muscle. The name "trochlear" is derived from the "trochlea," a pulley-like structure in the superior-medial orbit through which the superior oblique tendon passes. When the SO muscle contracts, it primarily causes **intorsion**, depression (in adduction), and abduction of the eye. ### 2. Explanation of Incorrect Options * **Oculomotor nerve (CN III):** This nerve supplies the majority of the extraocular muscles, including the Superior Rectus, Inferior Rectus, Medial Rectus, and Inferior Oblique, as well as the Levator Palpebrae Superioris (LPS). * **Trigeminal nerve (CN V):** This is a sensory nerve for the face and eye (Ophthalmic division - V1) and a motor nerve for the muscles of mastication. It does not provide motor supply to extraocular muscles. * **Abducens nerve (CN VI):** This nerve exclusively supplies the **Lateral Rectus (LR)** muscle, which is responsible for abduction (moving the eye outward). ### 3. Clinical Pearls for NEET-PG * **Longest & Slenderest:** CN IV has the longest intracranial course and is the thinnest cranial nerve, making it highly susceptible to trauma. * **Dorsal Exit:** It is the only cranial nerve that exits from the **dorsal aspect** of the brainstem. * **CN IV Palsy:** Patients typically present with **vertical diplopia** and a compensatory **head tilt** to the opposite side (Bielschowsky head tilt test) to minimize the double vision caused by the loss of intorsion.

Question 174: Damage to the trochlear nerve causes palsy of which extraocular muscle?

A. Superior Oblique (Correct Answer)
B. Lateral Rectus
C. Inferior Oblique
D. Inferior Rectus

Explanation: **Explanation:** The **Trochlear Nerve (Cranial Nerve IV)** is the smallest cranial nerve but has the longest intracranial course. It exclusively innervates the **Superior Oblique (SO)** muscle. A simple mnemonic used in ophthalmology to remember the nerve supply of extraocular muscles is **LR6(SO4)3**: * **LR6:** Lateral Rectus is supplied by CN VI (Abducens). * **SO4:** Superior Oblique is supplied by CN IV (Trochlear). * **3:** All other extraocular muscles (SR, IR, MR, IO) and the levator palpebrae superioris are supplied by CN III (Oculomotor). **Analysis of Options:** * **A. Superior Oblique (Correct):** As per the SO4 rule, CN IV supplies this muscle. Its primary action is intorsion; secondary is depression (in adduction). * **B. Lateral Rectus:** This is supplied by the **Abducens nerve (CN VI)**. Palsy results in medial squint (esotropia). * **C. Inferior Oblique:** This is supplied by the **Inferior division of the Oculomotor nerve (CN III)**. * **D. Inferior Rectus:** This is also supplied by the **Inferior division of the Oculomotor nerve (CN III)**. **Clinical Pearls for NEET-PG:** 1. **Longest & Slenderest:** CN IV has the longest intracranial course and is the only cranial nerve to exit from the **dorsal aspect** of the brainstem. 2. **Clinical Presentation:** Patients with IV nerve palsy present with **vertical diplopia** (worse on downgaze) and often adopt a **compensatory head tilt** to the opposite side of the lesion to minimize double vision. 3. **Bielschowsky Head Tilt Test:** This is the diagnostic clinical test used to confirm SO palsy; the vertical deviation increases when the head is tilted toward the affected side.

Question 175: All of the following can cause optic neuritis, except?

A. Rifampicin (Correct Answer)
B. Digoxin
C. Chloroquine
D. Ethambutol

Explanation: **Explanation:** The correct answer is **A. Rifampicin**. Optic neuritis (or toxic optic neuropathy) is a common side effect of several systemic medications, but Rifampicin is not typically associated with optic nerve toxicity. Its primary ocular side effect is the harmless **orange-red discoloration of tears**, sweat, and urine. **Analysis of Options:** * **Ethambutol (Option D):** This is the most classic cause of drug-induced optic neuropathy. It causes a dose-dependent **retrobulbar neuritis**, typically affecting the central fibers of the optic nerve, leading to decreased visual acuity and **red-green color blindness**. * **Chloroquine (Option C):** While primarily known for causing "Bull’s eye maculopathy," chloroquine and hydroxychloroquine can also lead to optic nerve atrophy and toxic neuropathy in long-term users. * **Digoxin (Option B):** Digoxin toxicity is famous for causing **chromatopsia** (specifically xanthopsia or yellow-tinted vision). It exerts toxic effects on both the retina (cones) and the optic nerve. **High-Yield Clinical Pearls for NEET-PG:** * **Ethambutol Monitoring:** Patients on Ethambutol should undergo baseline and monthly visual acuity and color vision (Ishihara chart) testing. It is contraindicated in children who are too young for subjective visual assessment. * **Other Drugs causing Optic Neuritis:** Isoniazid (INH), Amiodarone, Linezolid, Methanol, and Chloramphenicol. * **Amiodarone:** Can cause both optic neuropathy and **vortex keratopathy** (cornea verticillata). * **Methanol:** Characteristically causes "snowstorm vision" and optic disc hyperemia followed by atrophy.

Question 176: Attitudinal field defect is seen in which of the following conditions?

A. Optic nerve lesion
B. Optic neuritis
C. Lesions of the occipital lobe
D. Anterior ischemic optic neuropathy (Correct Answer)

Explanation: **Explanation:** An **altitudinal field defect** is a visual field loss that respects the horizontal midline, involving either the entire upper or lower half of the visual field. **1. Why Anterior Ischemic Optic Neuropathy (AION) is correct:** AION is the most common cause of altitudinal defects. The blood supply to the optic nerve head is provided by the **short posterior ciliary arteries (SPCAs)**. These arteries are arranged in a segmental fashion, typically dividing the optic disc into superior and inferior halves. When an infarction occurs in one of these segments, it leads to ischemia of either the upper or lower portion of the nerve, resulting in a corresponding inferior or superior altitudinal field loss (most commonly inferior). **2. Why the other options are incorrect:** * **Optic nerve lesion:** While AION is a type of optic nerve lesion, "optic nerve lesion" is a broad category. General trauma or compression usually results in central, cecocentral, or arcuate scotomas rather than a strict altitudinal defect. * **Optic neuritis:** Typically presents with a **central or cecocentral scotoma**. It is characterized by painful vision loss and is strongly associated with Multiple Sclerosis. * **Lesions of the occipital lobe:** These typically cause **homonymous hemianopia** (respecting the vertical midline) or cortical blindness. While a lesion of the lingual gyrus or cuneus could theoretically cause a quadrantanopia, it does not typically present as a classic altitudinal defect. **Clinical Pearls for NEET-PG:** * **AION Types:** Differentiate between **Arteritic (Giant Cell Arteritis)** and **Non-arteritic (NAION)**. NAION is often associated with a "crowded disc" (disc at risk). * **Differential Diagnosis:** Besides AION, altitudinal defects can also be seen in **Hemiretinal Vein Occlusion (HRVO)** or advanced **Glaucoma**. * **Rule of Thumb:** If a field defect respects the **horizontal** midline, think pre-chiasmal (Retina/Optic Nerve). If it respects the **vertical** midline, think chiasmal or post-chiasmal.

Question 177: A patient complains of difficulty reading, and careful testing of their visual fields demonstrates a central scotoma involving one visual field. This defect is MOST likely due to a lesion involving which of the following structures?

A. Macula (Correct Answer)
B. Optic chiasm
C. Optic radiations in the parietal lobe
D. Optic radiations in the temporal lobe

Explanation: ### Explanation **1. Why the Correct Answer is Right:** A **central scotoma** is a defect involving the central point of fixation. The **macula** (specifically the fovea) is responsible for high-acuity central vision and fine detail required for tasks like reading. A lesion involving the macula or the papillomacular bundle (the nerve fibers carrying information from the macula to the optic nerve) results in a **unilateral central scotoma**. Because the question specifies the defect involves "one visual field," it points toward a pre-chiasmal, ocular structure like the macula. **2. Why the Incorrect Options are Wrong:** * **Optic Chiasm:** Lesions here typically cause **bitemporal hemianopia** (loss of peripheral vision in both eyes) due to the decussation of nasal retinal fibers. * **Optic Radiations (Parietal Lobe):** Lesions in the parietal fibers (superior radiations) result in an **inferior homonymous quadrantanopia** ("pie on the floor"). * **Optic Radiations (Temporal Lobe):** Lesions in Meyer’s loop (inferior radiations) result in a **superior homonymous quadrantanopia** ("pie in the sky"). * *Note:* Post-chiasmal lesions (C and D) always cause bilateral, homonymous defects, not a defect in just "one visual field." **3. High-Yield Clinical Pearls for NEET-PG:** * **Unilateral field defects** are always **pre-chiasmal** (Retina or Optic Nerve). * **Bilateral field defects** are **chiasmal or post-chiasmal**. * **Centrocecal scotoma:** A defect involving both the central fixation point and the physiological blind spot; classic for toxic/nutritional optic neuropathy (e.g., Ethambutol toxicity, Tobacco-alcohol amblyopia). * **Macular Sparing:** Seen in posterior cerebral artery (PCA) occlusion affecting the occipital cortex, because the macular representation has a dual blood supply (PCA and Middle Cerebral Artery).

Question 178: Ocular bobbing is typically associated with lesions in which part of the brainstem?

A. Midbrain
B. Pons (Correct Answer)
C. Medulla
D. Cortex

Explanation: **Explanation:** **Ocular bobbing** is a classic clinical sign characterized by a rapid downward movement of the eyes followed by a slow, drifting return to the primary position. 1. **Why the Pons is correct:** Ocular bobbing is a specific localizing sign for **destructive lesions of the caudal pons**, most commonly a large pontine hemorrhage, infarct, or tumor. The pathophysiology involves the destruction of the **Paramedian Pontine Reticular Formation (PPRF)**, which abolishes horizontal eye movements. This allows the vertical ocular generators (located in the midbrain) to act unopposed, resulting in the characteristic vertical "bobbing" motion. It is typically seen in comatose patients. 2. **Why other options are incorrect:** * **Midbrain:** Lesions here typically cause **Parinaud Syndrome** (upgaze palsy) or **Ocular Dipping** (slow down, fast up), which is the inverse of bobbing and often follows global anoxia. * **Medulla:** Medullary lesions are associated with **Upbeat or Downbeat nystagmus**, but not the rhythmic "fast-down, slow-up" pattern of bobbing. * **Cortex:** Cortical lesions (e.g., frontal eye fields) cause a horizontal gaze preference toward the side of the lesion, not vertical bobbing. **High-Yield Clinical Pearls for NEET-PG:** * **Ocular Bobbing:** Fast down, slow up (Pons). * **Ocular Dipping:** Slow down, fast up (Diffuse encephalopathy/Anoxia). * **Reverse Bobbing:** Slow down, fast up (but in patients with intact horizontal movements). * **Key Association:** If you see "Pinpoint pupils + Hyperpyrexia + Ocular bobbing," the diagnosis is almost always **Pontine Hemorrhage**.

Question 179: In optic atrophy, pallor of the optic disc is an index of which of the following?

A. Degeneration of optic nerve fibers
B. Loss of vascularity of the optic disc (Correct Answer)
C. Demyelination of the optic nerve fibers
D. All of the above

Explanation: **Explanation:** The characteristic white or pale appearance of the optic disc in optic atrophy is primarily a result of the **loss of vascularity**. **1. Why the correct answer is right:** The normal pinkish hue of the optic disc is derived from the capillary network (the prelaminar capillaries) and the underlying vasculature. In optic atrophy, there is a secondary reduction in the blood supply following the loss of axons. As the nerve fibers disappear, the capillary bed shrinks, and there is an increase in glial tissue (astrogliosis). The combination of **decreased perfusion** and the **altered light-reflecting properties** of the glial tissue results in the clinical appearance of pallor. Therefore, pallor is an index of vascularity, not necessarily the exact degree of fiber loss. **2. Why the other options are incorrect:** * **Degeneration of optic nerve fibers:** While fiber degeneration is the *cause* of optic atrophy, the pallor itself is a vascular sign. You can have significant fiber loss before pallor becomes clinically evident (and vice versa). * **Demyelination:** This refers to the loss of the myelin sheath (e.g., in Multiple Sclerosis). While demyelination can lead to atrophy, it is the subsequent loss of axons and blood vessels that causes the pallor, not the demyelination process itself. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Optic Atrophy:** Disc is pale with clear margins (e.g., Pituitary tumor, MS). * **Secondary Optic Atrophy:** Disc is pale with dirty/blurred margins due to previous papilledema. * **Consecutive Optic Atrophy:** Follows retinal diseases like Retinitis Pigmentosa or Central Retinal Artery Occlusion (CRAO). * **Kestenbaum’s Index:** A clinical test where the number of capillaries crossing the disc margin is counted (Normal: 10; Atrophy: <6).

Question 180: All of the following are true for Adie's tonic pupil, except?

A. Light reflex is present (Correct Answer)
B. It is usually unilateral
C. The affected pupil is larger
D. Near reflex is very slow and tonic

Explanation: ### Explanation **Adie’s Tonic Pupil** is a clinical condition caused by post-ganglionic denervation of the **ciliary ganglion** (often due to a viral infection). Understanding the "Light-Near Dissociation" is key to solving this question. **1. Why Option A is the correct answer (The "Except"):** In Adie’s pupil, the **Light Reflex is absent or severely sluggish**. This occurs because the parasympathetic fibers responsible for pupillary constriction are damaged. Therefore, the statement "Light reflex is present" is false. **2. Analysis of Incorrect Options:** * **Option B (Usually unilateral):** In the acute phase, 80% of cases are unilateral. Over time, it may become bilateral (at a rate of 4% per year), but "usually unilateral" is a correct clinical description. * **Option C (Affected pupil is larger):** Because the parasympathetic supply to the sphincter pupillae is lost, the pupil remains **dilated (Mydriasis)** and fails to constrict to light, making it larger than the normal eye. * **Option D (Near reflex is slow and tonic):** This is a hallmark feature. While the light reflex is lost, the near reflex is preserved but occurs very slowly (tonic) due to **aberrant regeneration** of ciliary fibers. **3. High-Yield Clinical Pearls for NEET-PG:** * **Segmental Palsy:** On slit-lamp examination, you may see "worm-like" (vermiform) movements of the iris. * **Pharmacology Test:** Adie’s pupil shows **denervation supersensitivity**. It constricts with **dilute Pilocarpine (0.125%)**, whereas a normal pupil will not. * **Holmes-Adie Syndrome:** When Adie’s pupil is associated with **absent deep tendon reflexes** (usually the ankle jerk). * **Demographics:** Most commonly seen in young females.

Practice by Chapter

Anatomy of Visual Pathways

Practice Questions

Pupillary Disorders

Practice Questions

Optic Neuritis

Practice Questions

Ischemic Optic Neuropathies

Practice Questions

Other Optic Neuropathies

Practice Questions

Papilledema

Practice Questions

Cranial Nerve Palsies

Practice Questions

Nystagmus

Practice Questions

Visual Field Defects

Practice Questions

Neuro-ophthalmic Manifestations of Intracranial Lesions

Practice Questions

Functional Visual Disorders

Practice Questions

Migraine and the Eye

Practice Questions

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