Neuro-Ophthalmic Disorders & Visual Function Testing Flashcards

Which cranial nerve is affected in third nerve palsy?

Answer: Oculomotor nerve (III)

The oculomotor nerve (cranial nerve III) innervates most of the extraocular muscles (medial rectus, superior rectus, inferior rectus, inferior oblique) and the levator palpebrae superioris muscle (which lifts the eyelid). Therefore, a third nerve palsy affects multiple eye movements, causing the eye to be down and out, and often results in ptosis (drooping eyelid) and a dilated pupil.

Which test is most appropriate for evaluating visual field defects?

Answer: Perimetry

Perimetry, also known as visual field testing, specifically maps out the entire area of vision, including central and peripheral fields. It is designed to detect and quantify areas of vision loss or blind spots (scotomas) that indicate damage to the visual pathway, making it the most appropriate test for evaluating visual field defects.

A patient presents with bitemporal hemianopia. Where is the lesion most likely located?

Answer: Optic chiasm

Bitemporal hemianopia is a visual field defect characterized by loss of vision in the outer (temporal) half of both visual fields. This specific pattern of vision loss occurs when there is damage to the optic chiasm, where the nasal (temporal visual field) fibers from both optic nerves cross. A lesion here interrupts the transmission of information from the temporal visual fields of both eyes.

Which of the following is a hallmark sign of Horner’s syndrome?

Answer: Ptosis and miosis

Horner's syndrome results from damage to the sympathetic nerve supply to the eye and face. The classic triad of symptoms includes partial ptosis (drooping of the upper eyelid), miosis (constricted pupil), and anhidrosis (decreased sweating on the affected side of the face). Ptosis and miosis are the most consistently observed and defining ocular signs.

What is the function of the swinging flashlight test?

Answer: Identify RAPD

The swinging flashlight test is used to detect a Relative Afferent Pupillary Defect (RAPD), also known as a Marcus Gunn pupil. An RAPD indicates asymmetric damage to the afferent (sensory) visual pathway, typically in the optic nerve, where one optic nerve transmits less light signal than the other. This test helps localize the side of optic nerve dysfunction.

What condition is characterized by sudden, painless vision loss and a pale retina with a cherry-red spot?

Answer: CRAO

Central Retinal Artery Occlusion (CRAO) is a medical emergency caused by a blockage in the central retinal artery, leading to acute ischemia of the inner retina. The sudden, painless vision loss is characteristic, and ophthalmoscopic examination reveals a pale, edematous retina due to lack of blood flow, with a distinct cherry-red spot at the fovea where the choroidal circulation is visible.

Which test assesses contrast sensitivity in visual function testing?

Answer: Pelli-Robson chart

The Pelli-Robson chart is specifically designed to measure contrast sensitivity, which is the ability to distinguish between an object and its background. Unlike Snellen charts that measure high-contrast visual acuity, the Pelli-Robson chart presents letters of decreasing contrast, providing a more comprehensive assessment of visual function, especially in conditions affecting the optic nerve or retina.

What is optic neuritis commonly associated with?

Answer: Multiple sclerosis

Optic neuritis is inflammation of the optic nerve, often causing sudden, painful vision loss and reduced color vision. It is strongly associated with multiple sclerosis (MS), as it is frequently the initial symptom or a recurrent manifestation of demyelination in the central nervous system characteristic of MS.

Which visual field defect is typically associated with a lesion in the left occipital lobe?

Answer: Right homonymous hemianopia

The left occipital lobe processes visual information from the right half of the visual field for both eyes. Therefore, a lesion in the left occipital lobe will result in a loss of vision in the entire right half of the visual field, affecting both eyes, which is known as a right homonymous hemianopia. This defect occurs contralateral to the lesion.