Free ABO Neuro-Ophthalmology Questions and Answers — Questions and Answers
Question 1: Which cranial nerve palsy most commonly causes vertical diplopia?
- Oculomotor nerve (CN III)
- Trochlear nerve (CN IV) (Correct answer)
- Abducens nerve (CN VI)
- Optic nerve (CN II)
Correct answer: Trochlear nerve (CN IV)
The trochlear nerve (CN IV) innervates the superior oblique muscle, which primarily depresses and intorts the eye. A palsy of this nerve weakens the superior oblique, leading to an inability to depress the eye, especially when adducted. This results in vertical diplopia, often worse when looking down or reading, and patients may adopt a head tilt to compensate.
Question 2: What is the most common cause of a relative afferent pupillary defect (RAPD)?
- Glaucoma
- Optic neuritis (Correct answer)
- Cataract
- Conjunctivitis
Correct answer: Optic neuritis
A relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil, indicates a lesion in the afferent visual pathway anterior to the optic chiasm. Optic neuritis, an inflammation of the optic nerve, is a common cause, as it impairs the nerve's ability to transmit light signals effectively from the affected eye to the brain, leading to a diminished pupillary constriction response.
Question 3: Which condition is characterized by transient visual loss in one eye described as a 'curtain' descending?
- Papilledema
- Amaurosis fugax (Correct answer)
- Retinal detachment
- Macular degeneration
Correct answer: Amaurosis fugax
Amaurosis fugax describes a transient, monocular (one eye) visual loss, often characterized by a 'curtain' descending or ascending over the field of vision. It is typically caused by temporary ischemia to the retina or optic nerve, often due to an embolus from carotid artery disease or cardiac sources. This symptom warrants urgent investigation as it can be a warning sign of an impending stroke.
Question 4: Which finding is most consistent with Horner's syndrome?
- Mydriasis
- Ptosis and miosis (Correct answer)
- Exophthalmos
- Strabismus
Correct answer: Ptosis and miosis
Horner's syndrome results from a disruption of the sympathetic nerve pathway to the eye and face. The classic triad includes ptosis (drooping of the upper eyelid due to denervation of Müller's muscle), miosis (constricted pupil due to denervation of the dilator pupillae muscle), and anhidrosis (decreased sweating on the affected side of the face). These signs collectively indicate sympathetic dysfunction.
Question 5: Which test is most appropriate to confirm papilledema?
- Fundus photography
- Tonometry
- Fluorescein angiography
- Lumbar puncture (Correct answer)
Correct answer: Lumbar puncture
Papilledema is swelling of the optic disc due to increased intracranial pressure (ICP). While fundus photography can document the appearance, a lumbar puncture is the definitive test to measure cerebrospinal fluid (CSF) pressure and confirm elevated ICP, which is the underlying cause of papilledema. This helps differentiate true papilledema from pseudopapilledema or other optic disc anomalies.
Question 6: What is the most common visual field defect in pituitary adenoma?
- Central scotoma
- Homonymous hemianopia
- Bitemporal hemianopia (Correct answer)
- Altitudinal defect
Correct answer: Bitemporal hemianopia
A pituitary adenoma typically grows superiorly from the sella turcica, compressing the optic chiasm. The optic chiasm is where nasal retinal fibers from both eyes cross, carrying information from the temporal visual fields. Compression of these crossing fibers leads to a characteristic bitemporal hemianopia, meaning loss of vision in the outer half of both visual fields.
Free ABO Neuro-Ophthalmology Questions and Answers
Which cranial nerve palsy most commonly causes vertical diplopia?