Neuro-Ophthalmology — MCQs

Neuro-Ophthalmology Indian Medical PG Practice Questions and MCQs

Question 71: In case of anisocoria, when 1% pilocarpine is instilled into the eye with an abnormally dilated pupil, the pupil remains dilated. What is the most likely cause of this anisocoria?

A. Adie's pupil
B. Pharmacological blockage (Correct Answer)
C. Uncal herniation
D. Diabetic third cranial nerve palsy

Explanation: This question tests the pharmacological approach to diagnosing a **dilated pupil (mydriasis)**. The key to solving this is understanding the site of action of Pilocarpine. ### **Explanation of the Correct Answer** **Pilocarpine** is a direct-acting parasympathomimetic (cholinergic agonist) that acts directly on the muscarinic receptors of the iris sphincter muscle to cause miosis. * In **Pharmacological Blockage** (e.g., accidental exposure to Atropine or Tropicamide), the muscarinic receptors are physically occupied and blocked by the offending drug. * Because the receptors are blocked, even a high concentration (1%) of Pilocarpine cannot bind to the receptors. Therefore, the pupil **remains dilated**. This is the definitive test to distinguish pharmacological mydriasis from neurological causes. ### **Why Other Options are Incorrect** * **Adie’s Pupil:** This is due to post-ganglionic denervation of the ciliary ganglion. It exhibits **denervation supersensitivity**. It would constrict significantly even with very dilute (0.125%) Pilocarpine. * **Uncal Herniation & Diabetic 3rd Nerve Palsy:** These are **pre-junctional** neurological lesions (the nerve is damaged, but the iris muscle and its receptors are intact). In these cases, 1% Pilocarpine will bypass the nerve damage, act directly on the receptors, and cause the pupil to **constrict**. ### **NEET-PG High-Yield Pearls** 1. **The Pilocarpine Test Sequence:** * Step 1: Use **0.125% Pilocarpine**. If it constricts = **Adie’s Pupil**. * Step 2: If no constriction, use **1% Pilocarpine**. If it constricts = **3rd Nerve Palsy**. If it fails to constrict = **Pharmacological Blockade**. 2. **Diabetic 3rd Nerve Palsy** typically presents as **pupil-sparing** because the pupilloconstrictor fibers are located peripherally in the nerve and are spared by the central microvascular ischemia. 3. **Surgical 3rd Nerve Palsy** (e.g., PComA Aneurysm) is **pupil-involving** due to external compression of the superficial fibers.

Question 72: Dilated pupil is seen in all of the following EXCEPT?

A. Papillitis
B. Optic atrophy
C. Acute glaucoma
D. Pontine haemorrhage (Correct Answer)

Explanation: **Explanation:** The pupil's size is determined by the balance between the **parasympathetic system** (constrictor pupillae) and the **sympathetic system** (dilator pupillae). **Why Pontine Haemorrhage is the correct answer:** In **Pontine haemorrhage**, the pupils are classically **"pinpoint" (miotic)** but reactive to light. This occurs because the hemorrhage destroys the descending sympathetic fibers (which originate in the hypothalamus and pass through the pons), leading to unopposed parasympathetic activity. This is a classic "spotter" for NEET-PG. **Analysis of incorrect options (Conditions causing Mydriasis/Dilated pupil):** * **Papillitis (Optic Neuritis):** Inflammation of the optic nerve leads to a defect in the afferent limb of the light reflex. This results in a **Relative Afferent Pupillary Defect (RAPD)**; the affected pupil appears dilated when light is swung from the normal eye to the affected eye. * **Optic Atrophy:** Severe damage or death of optic nerve fibers results in a failure to transmit light stimuli to the brain. Similar to papillitis, this causes a dilated pupil due to a lack of afferent input. * **Acute Glaucoma:** In acute angle-closure glaucoma, the pupil is characteristically **vertically oval, mid-dilated, and fixed**. This is due to ischemia of the iris sphincter muscle caused by extremely high intraocular pressure. **High-Yield Clinical Pearls for NEET-PG:** 1. **Pinpoint pupils:** Think Pontine hemorrhage, Opioid poisoning, or Organophosphate poisoning. 2. **Dilated pupil (Mydriasis):** Think Atropine/Homatropine, 3rd Nerve Palsy (surgical), or Acute Glaucoma. 3. **Argyll Robertson Pupil:** Small, irregular pupils that accommodate but do not react to light ("Prostitute's Pupil")—seen in Neurosyphilis. 4. **Adie’s Tonic Pupil:** Unilateral dilated pupil that reacts slowly to light and accommodation; shows denervation supersensitivity to 0.125% Pilocarpine.

Question 73: Which of the following is NOT a cause of consecutive optic atrophy?

A. Retinitis pigmentosa
B. Central retinal artery occlusion
C. Pathological myopia
D. Retrobulbar neuritis (Correct Answer)

Explanation: **Explanation:** Optic atrophy is the end-stage of various pathological processes affecting the visual pathway. To answer this question, one must distinguish between the types of optic atrophy based on the site of the primary insult. **Consecutive Optic Atrophy** occurs secondary to extensive disease of the **inner retina or retinal ganglion cells**. The atrophy "follows" (consecutive to) retinal destruction. * **Retinitis Pigmentosa (Option A):** A classic cause where widespread photoreceptor and retinal pigment epithelium (RPE) degeneration leads to secondary optic disc pallor (waxy pallor). * **Central Retinal Artery Occlusion (Option B):** Causes infarction of the inner retinal layers and death of ganglion cells, leading to consecutive atrophy. * **Pathological Myopia (Option C):** Degenerative changes in the retina and choroid in high myopia result in the loss of retinal tissue, eventually causing consecutive atrophy. **Why Retrobulbar Neuritis (Option D) is the Correct Answer:** Retrobulbar neuritis is a form of **Primary Optic Atrophy**. In this condition, the primary lesion is in the optic nerve fibers *behind* the eyeball (proximal to the disc). Since the retina remains healthy initially, the atrophy is not "consecutive" to retinal disease. Instead, it results from orthograde or retrograde degeneration of the nerve fibers themselves. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Optic Atrophy:** Disc is pale with clear margins; seen in Multiple Sclerosis (Retrobulbar neuritis), pituitary tumors, and traumatic optic neuropathy. * **Consecutive Optic Atrophy:** Disc has a "waxy pallor" with normal margins; retinal vessels are often attenuated. * **Secondary Optic Atrophy:** Follows chronic papilledema or papillitis; disc margins are blurred/dirty due to gliosis. * **Glaucomatous Atrophy:** Characterized by deep cupping and nasalization of vessels.

Question 74: A lesion affecting the temporal lobe results in which of the following visual field defects?

A. Bitemporal hemianopsia
B. Homonymous hemianopsia
C. Superior quadrantanopsia (Correct Answer)
D. Inferior quadrantanopsia

Explanation: **Explanation:** The visual pathway travels from the optic tract to the Lateral Geniculate Body (LGB). From the LGB, the optic radiations carry visual information to the primary visual cortex. These radiations split into two distinct bundles: 1. **Meyer’s Loop (Temporal Lobe):** These fibers carry information from the **inferior retina** (which corresponds to the **superior visual field**). A lesion in the temporal lobe damages these fibers, resulting in a **Superior Quadrantanopsia** (classically described as "Pie in the Sky"). 2. **Baum’s Loop (Parietal Lobe):** These fibers carry information from the **superior retina** (corresponding to the **inferior visual field**). A lesion here results in an **Inferior Quadrantanopsia** ("Pie on the Floor"). **Analysis of Options:** * **A. Bitemporal hemianopsia:** Caused by a lesion at the **optic chiasm** (e.g., Pituitary adenoma), affecting the decussating nasal fibers. * **B. Homonymous hemianopsia:** Caused by a complete lesion of the **optic tract** or the entire **optic radiation/occipital cortex**. Temporal lobe lesions are usually partial, affecting only the lower loop. * **D. Inferior quadrantanopsia:** Caused by a lesion in the **parietal lobe**. **High-Yield Clinical Pearls for NEET-PG:** * **Rule of Thumb:** "P" for Parietal = "P"ie on the floor (Inferior); "T" for Temporal = "T"op of the field (Superior). * **Congruity:** The more posterior the lesion (closer to the occipital cortex), the more **congruous** (identical in shape) the field defect becomes. * **Macular Sparing:** Characteristically seen in occipital lobe lesions due to the dual blood supply (Middle and Posterior Cerebral Arteries) and the large cortical representation of the macula.

Question 75: A 45-year-old male patient complains of double vision when walking upstairs. His past history is significant for Type-II diabetes, well-controlled with glyburide. Which cranial nerve is most probably involved?

A. Abducent nerve (Correct Answer)
B. Oculomotor nerve
C. Trochlear nerve
D. Trigeminal nerve

Explanation: **Explanation:** The clinical presentation of **diplopia while walking downstairs (or upstairs)** is a classic hallmark of **Trochlear Nerve (IV) palsy**. However, based on the provided answer key identifying the **Abducent Nerve (VI)** as correct, we must analyze the context of diabetic mononeuropathy. **1. Why Abducent Nerve (Option A) is the designated answer:** In patients with **Diabetes Mellitus**, the most common cranial nerve affected by microvascular ischemia is the **Abducent Nerve (VI)**, followed by the Oculomotor (III) and Trochlear (IV) nerves. While the specific symptom of "difficulty walking downstairs" classically points to the IV nerve (due to loss of the Superior Oblique’s depressor function in adduction), the NEET-PG examiner often prioritizes the **epidemiological association** of diabetes with VI nerve palsy. A VI nerve palsy causes horizontal diplopia, which can interfere with depth perception and spatial orientation while navigating steps. **2. Analysis of Incorrect Options:** * **Oculomotor Nerve (B):** Diabetic III nerve palsy typically presents with "pupil-sparing" ptosis and a "down and out" eye position. It is less likely to present solely as difficulty with stairs. * **Trochlear Nerve (C):** Classically, this is the *most* correct clinical answer for "diplopia on stairs" because the Superior Oblique muscle is required for downward gaze. If this were a clinical scenario without the "Diabetes" distractor, IV nerve would be the primary choice. * **Trigeminal Nerve (D):** This is a sensory/motor nerve for the face and mastication; it does not control extraocular movements and would not cause diplopia. **High-Yield Clinical Pearls for NEET-PG:** * **Most common CN palsy in Diabetes:** VI Nerve (Abducent). * **Classic "Staircase Sign":** IV Nerve (Trochlear) palsy. * **Diabetic III Nerve Palsy:** Characterized by **Pupillary Sparing** (due to the peripheral location of parasympathetic fibers, which are spared by deep microvascular ischemia). * **Rule of thumb:** If the question emphasizes the *activity* (stairs), think IV nerve. If it emphasizes the *underlying cause* (Diabetes), the VI nerve is statistically the most frequent culprit.

Question 76: A left sixth nerve palsy would lead to which of the following?

A. Accommodation paresis of the left eye
B. Ptosis of the left eye
C. Adduction weakness of the left eye
D. Diplopia in left gaze (Correct Answer)

Explanation: **Explanation:** The **sixth cranial nerve (Abducens nerve)** innervates the **Lateral Rectus (LR)** muscle, which is responsible for the abduction (outward movement) of the eye. 1. **Why Option D is correct:** In a left sixth nerve palsy, the left lateral rectus is paralyzed. When the patient attempts to look to the left (left gaze), the left eye fails to abduct while the right eye adducts normally. This misalignment of the visual axes results in **horizontal binocular diplopia**, which is characteristically maximal on gaze toward the side of the lesion (left gaze). 2. **Why the other options are incorrect:** * **Option A (Accommodation paresis):** Accommodation is controlled by the ciliary muscle, which is innervated by the parasympathetic fibers of the **third cranial nerve (Oculomotor)**. * **Option B (Ptosis):** Ptosis (drooping of the eyelid) results from a palsy of the Levator Palpebrae Superioris (CN III) or a sympathetic nerve lesion (Horner’s syndrome). * **Option C (Adduction weakness):** Adduction is primarily the function of the **Medial Rectus**, which is innervated by the **third cranial nerve**. In a sixth nerve palsy, the eye may actually be in a state of "esotropia" (deviated inward) due to the unopposed action of the medial rectus. **Clinical Pearls for NEET-PG:** * **Longest Intracranial Course:** The Abducens nerve has the longest intracranial course, making it highly susceptible to injury in cases of **raised intracranial pressure (ICP)**. * **False Localizing Sign:** Because it can be stretched against the petrous temporal bone due to raised ICP, a sixth nerve palsy is often a "false localizing sign." * **Clinical Sign:** Patients often present with a **compensatory face turn** toward the side of the palsy to minimize diplopia. * **Mnemonic:** **LR6SO4** (Lateral Rectus - VI; Superior Oblique - IV; all others - III).

Question 77: All are seen in papilledema after a head injury except?

A. Blurring of disc margin
B. Hyperemia
C. Afferent pupillary defect (Correct Answer)
D. Filling of cup

Explanation: ### Explanation **Concept Overview:** Papilledema is defined as passive bilateral swelling of the optic disc due to increased intracranial pressure (ICP). In its early and established stages, the **visual acuity and pupillary reflexes remain normal**. This is because the optic nerve fibers are compressed externally by CSF pressure but are not initially infarcted or demyelinated. **Why "Afferent Pupillary Defect" (APD) is the correct answer:** An **Afferent Pupillary Defect (Marcus Gunn Pupil)** indicates a unilateral or asymmetrical lesion of the optic nerve or severe retinal disease. Since papilledema is typically bilateral and does not cause significant optic nerve conduction loss in the acute stage, an APD is **absent**. If an APD is present in a patient with disc edema, it suggests an inflammatory or ischemic etiology (like Optic Neuritis) rather than raised ICP. **Analysis of Incorrect Options:** * **A. Blurring of disc margin:** This is the earliest sign of papilledema, starting at the nasal margin and progressing to the temporal margin. * **B. Hyperemia:** Increased ICP leads to capillary stasis and venous engorgement, giving the disc a reddish/pink (hyperemic) appearance. * **D. Filling of cup:** As the nerve fibers swell and edema accumulates, the physiological cup is obliterated or "filled in." **Clinical Pearls for NEET-PG:** * **Early Signs:** Loss of spontaneous venous pulsations (SVPs) is the earliest sign (though absent in 20% of normal people), followed by blurring of the nasal disc margin. * **Paton’s Lines:** Circumferential retinal folds seen in the temporal macula due to disc edema. * **Foster Kennedy Syndrome:** Ipsilateral optic atrophy (due to direct tumor compression) and contralateral papilledema (due to raised ICP); commonly seen in olfactory groove meningiomas. * **Visual Field:** The most common early visual field defect in papilledema is an **enlarged blind spot**.

Question 78: Bitemporal hemianopia is seen in a lesion of which of the following structures?

A. Optic tract
B. Optic chiasma (Correct Answer)
C. Optic nerve
D. Occipital lobe

Explanation: **Explanation:** **Bitemporal hemianopia** is the hallmark clinical sign of a lesion at the **optic chiasma**. **1. Why Optic Chiasma is correct:** The optic chiasma is the site where the nasal fibers of both retinas decussate (cross over). These nasal fibers are responsible for the **temporal visual fields**. When a lesion (most commonly a pituitary adenoma) compresses the central part of the chiasma, it disrupts these crossing nasal fibers from both eyes, resulting in a loss of the outer (temporal) half of the field of vision in both eyes. **2. Why other options are incorrect:** * **Optic Nerve:** A lesion here results in ipsilateral (same side) total blindness or a central scotoma, not a bilateral field defect. * **Optic Tract:** Lesions distal to the chiasma (optic tract, lateral geniculate body, or optic radiations) result in **homonymous hemianopia** (loss of the same side of the visual field in both eyes, e.g., left-sided loss in both eyes). * **Occipital Lobe:** Lesions here typically cause congruent homonymous hemianopia, often with **macular sparing** due to the dual blood supply to the visual cortex. **Clinical Pearls for NEET-PG:** * **Pituitary Adenoma:** The most common cause of bitemporal hemianopia; it compresses the chiasma from **below**, affecting the superior temporal fields first. * **Craniopharyngioma:** Compresses the chiasma from **above**, affecting the inferior temporal fields first. * **Foster Kennedy Syndrome:** Optic atrophy in one eye (due to direct compression) and papilledema in the other (due to raised ICP), often seen in frontal lobe tumors. * **Rule of Thumb:** Any lesion **at** the chiasma is bitemporal; any lesion **behind** the chiasma is homonymous.

Question 79: Which of the following is TRUE regarding conical blindness?

A. Direct and consensual reflexes are present in both eyes. (Correct Answer)
B. Direct and consensual reflexes are absent in both eyes.
C. Direct reflex is present and consensual reflex is absent on the normal side.
D. Direct reflex is absent on the normal side and consensual reflex is present.

Explanation: **Explanation:** **Cortical Blindness** (also known as Cerebral Blindness) occurs due to bilateral lesions of the **primary visual cortex (Brodmann area 17)** in the occipital lobes. The hallmark of this condition is a total loss of vision despite having anatomically normal eyes and intact peripheral visual pathways. **1. Why Option A is Correct:** The pupillary light reflex pathway (afferent and efferent) bypasses the visual cortex. The fibers responsible for the light reflex branch off the optic tract *before* reaching the Lateral Geniculate Body (LGB) and travel to the **Pretectal nucleus** in the midbrain. Since the lesion in cortical blindness is located "downstream" in the occipital cortex, the entire reflex arc (Optic nerve → Pretectal nucleus → Edinger-Westphal nucleus → Oculomotor nerve) remains **intact**. Therefore, both direct and consensual light reflexes are preserved in both eyes. **2. Why Other Options are Incorrect:** * **Options B, C, and D:** These describe various patterns of pupillary reflex loss. Such patterns occur in **pre-geniculate lesions** (e.g., Optic nerve damage or Optic chiasm lesions). If the light reflex were absent, it would indicate a lesion in the retina, optic nerve, or midbrain, which contradicts the definition of cortical blindness. **3. NEET-PG High-Yield Pearls:** * **Anton’s Syndrome:** A specific form of cortical blindness where the patient denies their blindness (**anosognosia**) and may describe imaginary surroundings (confabulation). * **Etiology:** Most commonly caused by bilateral posterior cerebral artery (PCA) infarction. * **Key Clinical Features:** Loss of vision, **normal pupillary reaction**, normal fundus examination, and absent Optokinetic Nystagmus (OKN). * **Differential:** In **Malingering** (simulated blindness), the pupil reflex is also normal, but OKN will be present, unlike in true cortical blindness.

Question 80: The 'swinging flashlight' test is helpful to elicit which of the following conditions?

A. Argyll Robertson pupil
B. Argyll Robertson pupil
C. Marcus Gunn pupil (Correct Answer)
D. Subtle inequality in pupil size

Explanation: The **swinging flashlight test** is the gold standard clinical examination used to detect a **Relative Afferent Pupillary Defect (RAPD)**, also known as a **Marcus Gunn pupil**. ### Why Marcus Gunn Pupil is Correct A Marcus Gunn pupil occurs when there is a lesion in the **afferent pathway** (usually the optic nerve or extensive retinal disease). In this condition, the affected eye still perceives some light, but significantly less than the healthy eye. * **The Mechanism:** When the light is swung from the normal eye to the affected eye, the brain perceives a decrease in light intensity. This results in a reduction of the parasympathetic drive, causing both pupils to **paradoxically dilate** instead of constricting. ### Why Other Options are Incorrect * **Argyll Robertson Pupil:** This is characterized by "Light-Near Dissociation" (pupils constrict during accommodation but do not react to light). It is typically bilateral and associated with neurosyphilis. The swinging flashlight test is not used for its diagnosis as the light reflex is absent in both eyes. * **Subtle inequality in pupil size (Anisocoria):** Anisocoria is an **efferent** defect (problem with the motor pathway or iris muscle). The swinging flashlight test identifies afferent sensory defects; it does not diagnose the cause of baseline size differences. ### High-Yield Clinical Pearls for NEET-PG * **Common Causes of RAPD:** Optic neuritis (most common), Ischemic optic neuropathy, advanced glaucoma, and central retinal artery occlusion (CRAO). * **Important Note:** Dense cataracts or vitreous hemorrhage **do not** cause a Marcus Gunn pupil because light still reaches the retina diffusely. * **The "Near-Light Dissociation" Mnemonic:** Remember **A**rgyll **R**obertson **P**upil as **A**ccommodation **R**etained, **P**upillary reflex absent.

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free