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Being called to
see a patient who suddenly complains of loss of vision in
one or both eyes can be daunting. Understandably, the
patient is often anxious, and you may be as well. The best
way to tackle the problem is the same as you would for any
other medical problem--start with the history and
examination. |
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Find out about
the timing of the visual loss--often it happens first thing
in the morning--and the onset of symptoms. Did the visual
loss last minutes or hours; did the patient wake up with the
problem? Beware of "acute" visual loss that is actually of
chronic duration but suddenly noticed by the patient; he or
she may not be aware of visual loss in one eye until the
other eye is occluded--for example, when rubbing an eyelid.
Try to establish how severe the visual loss is, it can be
just blurring or no perception of light at all. Find out if
one or both eyes are affected. It sounds surprising, but
patients can mistake a homonymous heminanopia for complete
loss of vision in just one eye. |
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The loss of
vision may be so profound that Snellen acuity at 6 metres is
unrecordable, so you could try measuring from 3 metres. If
this does not work, see if the patient can count fingers or
detect hand movements. Failing that, record if the patient
can perceive light. Test colour vision; obviously a severe
visual defect may make this impossible. Testing visual
fields with this type of complaint, to exclude a homonymous
hemianopia, is essential. A positive relative afferent
pupillary defect when examining the pupils is an important
finding as it can represent pathology of the retina or
optic nerve.
When performing
ophthalmoscopy, remember to look for the red reflex first.
Then look at the fundus; is the disc swollen or pale? Does
the retina look pale? These suggest ischaemia, as with
elsewhere in the body. Is the retina full of haemorrhages
and cotton wool spots? |
