Examination of the Patient With Visual Symptoms

Monocular vision loss
may be transient or persistent. When patients present with transient
visual symptoms that they attribute to one eye, for you to be more
certain that your patient’s symptom was truly monocular and not a
hemianopic disturbance, the patient would have had to have covered the
bad eye during the event to confirm that the vision was intact in the
good eye. Some patients do initiate this test on their own during an
episode of vision loss, but you may need to specifically inquire if the
patient did this.

Patients with monocular visual problems
do not usually present with significant functional deficits from their
vision loss, as long as the remaining eye has intact visual fields. In
other words, unlike patients with hemianopsias, patients with purely
monocular vision loss are less likely to bump into objects because of
their visual dysfunction.

Amaurosis fugax (meaning fleeting blindness)
is an important kind of transient monocular vision loss that may be
seen in patients with retinal ischemia, such as can be associated with
carotid stenosis or temporal arteritis. Patients describe a brief
(seconds or minutes) loss of vision in

one eye as “like a shade coming down.” As the symptoms resolve, the patient may describe the shade coming back up.

Patients with optic neuritis usually
present with monocular vision loss that progresses over a period of
days and lasts for weeks, and it is often associated with pain on eye
movement.

Patients with visual field loss
often do not recognize the concept of a visual field or a visual field
deficit. They may misinterpret their homonymous visual field deficits
as monocular (i.e., a patient may interpret a left homonymous
hemianopsia as a visual problem involving the left eye alone).

Patients with hemianopic visual field
cuts sometimes present with symptoms of the consequences of their
deficits, rather than with a primary visual complaint. They may tell
you they consistently bump into objects on one side, or they may have
been involved in a motor vehicle collision because of their visual
deficit.

Patients with hemianopsias may present
with a vague visual complaint that they have difficulty describing.
Those with left homonymous hemianopsias may complain of difficulty
reading, not recognizing that their difficulty is due to consistently
missing the first (left) parts of sentences. Patients with bitemporal
field loss may complain of difficulty with their peripheral vision.

A common form of transient hemianopic
field deficit is the visual disturbance of a migraine aura. Migrainous
visual disturbances typically present as a scintillating (shining)
zigzag or herringbone-like pattern, sometimes in the form of a C,
occurring in the left or right visual field and gradually growing over
approximately a 15-minute period before resolving. This migrainous
visual disturbance may or may not be followed by a headache.

Patients with complete bilateral vision
loss due to bilateral occipital lobe infarcts can actually be unaware
that they are blind and deny the existence of their blindness. This is
known as Anton’s syndrome.

In patients with monocular vision loss
due to optic nerve dysfunction (such as optic neuritis), the visual
field in the affected eye may be a central scotoma. This is easily
detected by asking the patient to cover the good eye and look directly
at your face with the bad eye. The patient with a central scotoma
describes inability to see the central part of your face but is able to
see the periphery.

On pupillary examination, patients with
monocular vision loss due to optic nerve dysfunction also usually have
an afferent pupillary defect (see Chapter 10, Examination of the Pupils).

Acute monocular vision loss due to optic nerve demyelination or inflammation may be associated with optic disc swelling (see Fig. 11-2)
if the process involves the optic nerve head itself (papillitis);
however, the optic disc will appear normal if the disease process is
behind the eye (retrobulbar optic neuritis). Long-standing monocular
vision loss from severe optic nerve dysfunction is often associated
with significant pallor of the optic disc due to optic nerve atrophy
(see Fig. 11-4).

Patients with transient monocular vision
loss (amaurosis fugax) from carotid stenosis may or may not have other
evidence for carotid disease on examination, such as a bruit. They may
also rarely have refractile (bright) embolic material at the branch
points of one or several retinal arterioles visible on funduscopy,
called Hollenhorst plaques (Fig. 49-1).

In patients with symptoms suggestive of a visual field cut, confrontational visual field testing (see Chapter 13,
Visual Field Examination) will usually easily detect a deficit (i.e., a
left or right homonymous hemianopsia, quadrantanopsia, or bitemporal
hemianopsia).

Pupillary responses should be normal in
patients with hemianopic visual field deficits (as well as in patients
with complete vision loss due to bilateral occipital pathology) because
the lesion is posterior to the optic chiasm.