Ophthalmic Exam (continued)
Usually the eye is
initially examined in a darkened
area with a bright light. For
demonstration purposes, these
slides are taken in an area somewhat lighter than what one would normally use for an
ophthalmic examination. A
bright light such as a transilluminator or other halogen light source is
shone directly at the eye. This
allows one to assess the cornea for clarity and to look for any
abnormalities in the anterior aspect of the eye and the eyelids.
Also one can check the direct pupillary light response.
At the same time another observer can view the opposite eye for a
consensual light response. It
is important to keep the light source far enough from the eye so that if
the horse moves its head, it will not bump into the light.
Alternatively, when one wishes to look closer, one can use a finger or a
hand to guard the instrument and prevent the horse from traumatizing himself on it.
Horses' light responses may not be very rapid. A photophobic
response is usual in an eye that is visual.
Purkinje light reflections should be noted. When one moves the bright light horizontally, one sees three light
reflections; one from the cornea, one from the anterior lens, and one
rather dimmer light reflection from the posterior lens. The dimmer light reflection from the back of the lens moves in a
direction opposite to the other two light reflections which move in the
same direction that the handler is moving the light. Also, note that one should
stabilize one's hand
against the horse’s head when examining the eye with a light at very
close range so that
if the horse moves its head very rapidly, the handler will not
traumatize the horse’s eye with the light. Also, different angles can be used when viewing the eye with
a light so as to better assess abnormalities. Shining the light at different angles is also helpful when
a "beginner" is
trying to decide if a lesion is in the cornea or the lens.
||The other instrument that can be very helpful in
assessing the horse’s cornea is the magnifying lens that is on
the otoscope head. This
allows for very close examination of the cornea and magnifies lesions
therein. Then one should
proceed with using the ophthalmoscope.
Click here to
continue with the ophthalmic exam.....