Chapter 3 - Olfaction and Vision
Questions
Define the following terms:
anosmia,
homonomous,
hemianopsia,
quadrantanopsia,
scotoma,
papilledema,
papillitis,
optic neuritis.
Anosmia is a loss of the sense of smell (this can be unilateral or
bilateral).
Homonomous is a term referring to overlapping areas of the visual field
of each eye.
Hemianopsia (or hemianopia) is a loss of visual perception of one-half of the visual
world.
Quadrantanopsia is a loss of visual perception of one-quarter of the
visual world.
Scotoma is a patch of vision loss.
Papilledema is swelling of the optic nerve head usually produced by
congestion of the central retinal veins. This usually happens due to
increased intracranial pressure.
Papillitis is swelling of the optic nerve head due to inflammation.
Optic neuritis is inflammation of the optic nerve.
3-1. How do you
test olfaction?
Answer 3-1. Olfactory nerve is tested with aromatic compounds presented
to each nostril.
3-2. What is the
most common cause of unilateral anosmia?
Answer 3-2. Most common cause of unilateral anosmia is blockage of
nasal passage.
3-3. In whom is
it particularly important to test olfaction?
Answer 3-3. Olfactory testing is most important in patients with head
injury, mental status change and seizure.
3-4. How can you
determine if visual acuity problems are due to refractive or to nerve problems?
Answer 3-4. Visual acuity problems that are refractive improve with
pinhole testing (retinal or optic nerve problems do not).
3-5. What is the
significance of finding a monocular visual loss?
Answer 3-5. Assuming that this is not due to refractive problems in the
eyeball (usually ruled out by a funduscopic examination) monocular
problems are anterior to the optic chiasm (retina or optic nerves).
3-6. What is the
significance of finding a homonomous visual field deficit?
Answer 3-6. Homonymous visual field problems are posterior to the optic
chiasm.
3-7. Where would
a lesion that produced bitemporal hemianopsia be located?
Answer 3-7. Bitemporal hemianposia is often due to problems at the
optic chiasm (such as with pituitary tumors).
3-8. How can lesions
of the parietal or temporal lobes produce vision loss? What kind of loss would
you expect to find?
Answer 3-8. Optic radiations that pass from the thalamus to the visual
cortex in the occipital lobe either pass through the parietal lobe
(lower visual field) or through the temporal lobe (Meyer's loop - upper visual
field) - may produce quadrananopsia of either the contralateral lower
visual world (parietal lobe) or upper visual world (temporal lobe).
3-9. Where on the
visual cortex is the representation of the center of vision?
Answer 3-9. The center of vision is represented near the occipital pole
(often supplied by middle cerebral artery).
3-10. What artery
supplies the visual cortex?
Answer 3-10. Most of the visual cortex is supplied by posterior
cerebral arteries.
3-11. How can
you distinguish papilledema from papillitis (i.e., optic neuritis affecting the optic nerve head at the optic disc)?
Answer 3-11. The appearance is quite similar during ophthalmoscopy.
However, with papilledema, there is little change in vision (there
might be expansion of the physiologic blind spot) while papillitis is
associated with severe vision problems. Also, papilledema is likely to
be bilateral (this is uncommon in papillitis).