Chapter 40. Neuro-Ophthalmology: Afferent Visual System Flashcards
Question 40-1:
Visual field analysis of a patient reporting visual loss reveals
that the size of the visible field remains the same with
increasing distance, as shown in the figure:
Which is the correct diagnosis?
A. Optic neuritis
B. Glaucoma
C. Multiple sclerosis
D. Retinal vascular disease
E. Psychogenic visual loss
Answer 40-1: E.
Psychogenic visual loss has a number of potential clues, and one of the most reliable is from testing of visual fields. With increasing distance, the size of the visible field should increase, with the arc subtended by the visible field remaining the same. However. in many
patients with functional visual loss, there is the same absolute size of the field with increasing distance, such that the subtended arc is actually smaller. Compare the two figures below. (P732)
Question 40-2:
A patient presents with visual loss and is found on examination to have a bitemporal hemianopia. Which is the correct
conclusion?
A. The patient has a lesion at or near the chiasm
B. The patient has a lesion of the lateral geniculate
C. The patient has tandem lesions of both optic nerves
D. The localization cannot be determined from the supplied information
Answer 40-2: A.
True bitemporal hemianopia is caused by a lesion at the optic chiasm producing compression of the fibers from the nasal half of each eye which cross in the optic chiasm. (P733)
Question 40-3:
A patient presents with visual loss and is found on examination to have a complete homonymous hemianopia. Which is the correct conclusion regarding localization?
A. The lesion is of the occipital lobe
B. The lesion is of the parietal lobe and subcortical white
matter
C. The lesion is most likely at the lateral geniculate
D. The lesion can be anywhere between the chiasm and the occipital cortex
Answer 40-3: D.
A complete hemianopia is noLof as much help in localization as might be thought - the lesion can be anywhere from behind the chiasm to the occipital cortex. The main import is that the lesion is contralateral to visual field loss. Also, visual field deficit can be missed on routine examination. (P733)
Question 40-4:
Lesions of the optic tract are most likely to produce
hemianopia. In which localization are the defects likely
congruent rather than nonncongruent?
A. Anterior retrochiasmallesions
B. Posterior retrochiasmallesions
C. Chiasmal lesions
D. There is no localizing value to the congruence of the defect
Answer 40-4: B.
Lesions of the posterior retrochiasmal fibers are more likely to have congruent visual field loss whereas lesions of the anterior retrochiasmid are more likely to be incongruous. (P733)
Question 40-5:
Which of the following c1inicalfeatun:s can be seen in
albinism?
A Congenital nystagmus
B. Reduced visual activity
C. Hypoplasia of the fovea
D. Lack of stereopsis
E. All of these
Answer 40-5: E.
All of these can be seen in patients with albinism, including congenital nystagmus, reduced visual acuity, foveal hypoplasia, and lack of stereovision. In addition., there is abnormal crossing of about 20% of axons from the temporal retina (p738)
Question 40-6:
The figure shows the visual fields of a patient with complaints of left visual loss
Which is the most likely diagnosis?
A. Optic nerve compression
B. Optic neuritis
C. Psychogenic visual loss
D. Cannot be determined
Answer ~0-6: A.
Optic nerve compression produces unilateral visual field loss unless the compression is near the chiasm. Loss of peripheral field is typical of compression whereas optic neuritis produces central visual loss. (p733-735)
Question 40-7:
Ischemic optic neuropathy is most likely to produce which of
the following patterns of visual field loss?
A. Superior altitudinal defect
B. Inferior altitudinal defect
C. Centrocecal scotoma
D. Peripheral visual field loss
Answer 40-7: B.
Inferior altitudinal defect is the most likely manifestation of ischemic optic neuropathy although superior defect and total visual loss can occur. Centrocecal visual loss is more typical of optic neuritis, and peripheral visual field loss is typical of optic nerve compression. (P733)
Question 40-8:
The figure shows examination of the light responses of the pupils in what is called the “swinging-flashlight test.
What is the correct interpretation of the clinical findings?
A. Right afferent defect
B. Left afferent defect
C. Right partial third nerve palsy
D. Left partial third nerve palsy
Answer 40-8: A.
The patient has a right afferent pupillary defect - meaning that stimulation of the right eye fails to cause constriction of either eye, whereas stimulation of the left eye results in constriction of both eyes. The defect can be of the retina or optic nerve, but a lesion at or behind the chiasm would not be expected to produce this fmding. (P731)
Which of the following findings are suggestive of psychogenic visual loss?
1. Tunnel vision
2. Impaired optokinetic nystagmus
3. Spiral visual field
4. Abnormal YEP
Select: A = 1.2, 3. B = 1, 3 . C = 2. 4. D = 4 only. E = All
Answer 40-9: B.
Twmel vision and spiral vision ale two of the nonphysiologic patterns of visual loss which can develop in patients with psychogenic visual loss. YEP is usually normal despite the OKN response. (p735-737)
Question 40-10:
Which of the following are characteristic of Leber’s congenital
amaurosis ?
1. Association with Leber’s hereditary optic neuropathy in
more than half of cases
2. Salt and pepper appearance to the retina
3. Normal electroretinogram
4. Visual loss starting in childhood
Select: A = 1.2,3. B = 1.3. C= 2, 4. D: 4 only. E: All
Answer 40-10: C.
Leber’s congenital amaurosis is characterized by bilateral visual loss begilUling in early childhood, associated with a salt and pepper appearance to the retinal pigment epithelium. The eiectroretinogram is abnormal. There is no relationship between this disorder and Leber’s hereditary optic neuropathy. (P737)
