Ophthalmic Exam

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.

The 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.

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Copyright 1999-2001
New Bolton Center Field Service Department
Students:  Keith Javic - Class of 2003, C. Nikki Conroy - Class of 2003