Neuro-Ophthalmology Practice Questions

Q: What is true about optic nerve glioma?

Unilateral proptosis. **Optic Nerve Glioma** is a slow-growing, benign tumor (typically a juvenile pilocytic astrocytoma) that arises from the glial cells of the optic nerve. ### **Explanation of Options** * **D. Unilateral proptosis (Correct):** This is the hallmark clinical presentation. As the tumor grows within the optic canal or orbit, it pushes the globe forward. The proptosis is typically **axial** (straight forward) and **non-pulsatile**. * **A. Seen in old individuals:** Incorrect. This is primarily a disease of **childhood**, with 90% of cases diagnosed in the first two decades of life (peak age 2–6 years). In adults, optic nerve tumors are more likely to be malignant glioblastomas or meningiomas. * **B. Painful proptosis:** Incorrect. Optic nerve glioma causes **painless**, slowly progressive proptosis. Painful proptosis is more characteristic of inflammatory conditions (like orbital pseudotumor) or infections (orbital cellulitis). * **C. Can cause hematoma:** Incorrect. While some vascular tumors (like lymphangiomas) can cause sudden hemorrhage (chocolate cysts), gliomas do not typically present with hematoma. ### **High-Yield Clinical Pearls for NEET-PG** * **Association:** Strongly associated with **Neurofibromatosis Type 1 (NF-1)**. If bilateral optic nerve gliomas are present, NF-1 is almost certain. * **Imaging:** MRI shows a characteristic **fusiform (spindle-shaped) enlargement** of the optic nerve. A "kinking" or "buckling" of the nerve may also be seen. * **Visual Symptoms:** Gradual, painless loss of vision is common. On examination, look for an **Afferent Pupillary Defect (RAPD)** and optic atrophy or disc edema. * **Management:** Often follows a benign course; "observation" is preferred if vision is stable. Surgery or radiotherapy is reserved for progressive cases or intracranial extension.

Q: Waves present in electroretinogram are all EXCEPT:

d wave. **Explanation:** The **Electroretinogram (ERG)** is a diagnostic test that measures the electrical response of various cell layers in the retina to a light stimulus. A standard ERG waveform consists of three primary components: **a, b, and c waves.** * **Correct Answer (D):** The **d-wave** is not considered a standard component of the clinical ERG waveform. While some specialized research contexts refer to a "d-wave" as an "off-response" (occurring when the light stimulus is turned off), it is not part of the classic clinical ERG used to assess retinal function in standard examinations. **Analysis of Other Options:** * **A. a-wave:** This is the first **negative** deflection. It represents the activity of the **photoreceptors** (rods and cones) in the outer retinal layer. * **B. b-wave:** This is the large **positive** deflection following the a-wave. It is the most clinically significant wave and represents the health of the **inner retinal layers**, specifically the **Müller cells and Bipolar cells.** * **C. c-wave:** This is a prolonged, lower-amplitude positive wave following the b-wave. It originates from the **Retinal Pigment Epithelium (RPE)** in response to changes in subretinal potassium concentration. **High-Yield Clinical Pearls for NEET-PG:** * **Origin Summary:** a-wave (Photoreceptors), b-wave (Bipolar/Müller cells), c-wave (RPE). * **Oscillatory Potentials:** These are small ripples found on the ascending limb of the b-wave, originating from **Amacrine cells**. They are characteristically lost early in **Diabetic Retinopathy**. * **Negative ERG:** A condition where the a-wave is preserved but the b-wave is significantly reduced or absent. This is classically seen in **Central Retinal Artery Occlusion (CRAO)** and **Congenital Stationary Night Blindness (CSNB)**. * **EOG (Electro-oculogram):** Measures RPE function; the key parameter is the **Arden Index** (Normal > 1.8).

Q: All of the following are features of a tonic pupil, EXCEPT?

It is caused by damage to the oculomotor nerve. **Explanation:** The correct answer is **A (It is caused by damage to the oculomotor nerve)**. A tonic pupil (Adie’s Pupil) is caused by damage to the **ciliary ganglion** or the **short ciliary nerves**, not the main trunk of the oculomotor nerve (CN III). While CN III carries preganglionic parasympathetic fibers, the pathology in a tonic pupil is postganglionic. **Analysis of Options:** * **Option A (Incorrect Statement):** Damage to the oculomotor nerve typically results in a complete "blown pupil" with associated ptosis and motility deficits. In contrast, Adie’s pupil is an isolated pupillary abnormality due to postganglionic denervation. * **Option B (Correct Feature):** Damage to the ciliary ganglion affects the nerve supply to the ciliary muscle, leading to **accommodative paresis** (blurred near vision). * **Option C (Correct Feature):** Following denervation, the sphincter pupillae becomes hypersensitive to acetylcholine. This is the basis of the diagnostic test using **dilute Pilocarpine (0.125%)**, which constricts an Adie’s pupil but has no effect on a normal pupil. * **Option D (Correct Feature):** This describes **Light-Near Dissociation**. The pupil reacts poorly to light because of damaged fibers, but reacts slowly and "tonically" to near effort due to aberrant regeneration of fibers originally intended for the ciliary muscle. **High-Yield Clinical Pearls for NEET-PG:** * **Demographics:** Most common in young women; often unilateral (80%) but can become bilateral. * **Holmes-Adie Syndrome:** Adie’s pupil associated with **diminished deep tendon reflexes** (usually ankle jerks). * **Mnemonic:** "Adie’s is **A**dded (dilated) and **A**nkle jerks are down." * **Light-Near Dissociation (LND):** Other causes include Argyll Robertson Pupil (Neurosyphilis) and Parinaud Syndrome (Dorsal Midbrain Syndrome).

Q: A patient presents with limitation of abduction of the right eye and horizontal diplopia. Which cranial nerve is most likely affected?

Abducens nerve. **Explanation:** The clinical presentation of **limited abduction** and **horizontal diplopia** is the classic hallmark of a **6th Cranial Nerve (Abducens nerve) palsy**. **1. Why the Correct Answer is Right:** The Abducens nerve (CN VI) exclusively innervates the **Lateral Rectus (LR)** muscle. The primary action of the LR is abduction (moving the eye away from the midline). When this nerve is damaged, the LR fails to contract, leading to an inability to abduct the eye. This results in an "esotropia" (inward deviation) in the primary position, causing horizontal diplopia that worsens when the patient attempts to look toward the side of the lesion. **2. Why the Other Options are Incorrect:** * **Optic Nerve (CN II):** This is a purely sensory nerve responsible for vision and the light reflex. Damage causes vision loss or field defects, not ocular motility issues. * **Oculomotor Nerve (CN III):** This nerve innervates the MR, SR, IR, and IO muscles, as well as the levator palpebrae. A palsy would typically present with "Down and Out" eye positioning, ptosis, and potentially a dilated pupil, rather than isolated abduction failure. * **Trochlear Nerve (CN IV):** This nerve innervates the Superior Oblique. Damage causes **vertical/torsional diplopia** (worse on downgaze and tilting the head toward the lesion), not horizontal diplopia. **Clinical Pearls for NEET-PG:** * **Longest Intracranial Course:** The Abducens nerve has the longest intracranial course, making it highly susceptible to damage from increased intracranial pressure (**False Localizing Sign**). * **Mnemonic:** **LR6SO4** (Lateral Rectus-6, Superior Oblique-4; all others are 3). * **Nuclear Lesion:** A lesion in the Abducens nucleus (in the Pons) results in **ipsilateral horizontal gaze palsy** (inability of both eyes to look toward the lesion) due to involvement of interneurons to the contralateral Medial Rectus.

Question 1

Which of the following investigations is not necessary for evaluating optic neuritis?

Accepted Answer

Ultrasonography B-scan

Answer

MRI of the head and orbit

Answer

Erythrocyte Sedimentation Rate (ESR)

Answer

Visual fields assessment

Question 2

What is true about optic nerve glioma?

Accepted Answer

Unilateral proptosis

Answer

Seen in old individuals

Answer

Painful proptosis

Answer

Can cause hematoma

Question 3

Waves present in electroretinogram are all EXCEPT:

Accepted Answer

d wave

Answer

a wave

Answer

b wave

Answer

c wave

Question 4

All of the following are features of a tonic pupil, EXCEPT?

Accepted Answer

It is caused by damage to the oculomotor nerve

Answer

Accommodative paresis is present

Answer

Cholinergic supersensitivity of the denervated muscle is present

Answer

Reaction to light is absent and the reaction to near reflex is very slow and tonic

Question 5

A patient presents with limitation of abduction of the right eye and horizontal diplopia. Which cranial nerve is most likely affected?

Accepted Answer

Abducens nerve

Answer

Optic nerve

Answer

Oculomotor nerve

Answer

Trochlear nerve

Neuro-Ophthalmology — MCQs

Neuro-Ophthalmology — MCQs

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