Purkinjee Trees are an entoptic phenomenon of the eye's visual system.  When your Columbus Optometrists shines a bright indirect light into your eye you may see lines above and below the light.  These lines are shadows of the eye's blood vessels that cast a shadow on the retina.  

If you look directly at the Doctor's light you will only see the lines above and below where you are looking.  This is because the maculae's fovea, the center of your vision, does not have any blood vessels in it.

This test is used by Optometrists and Ophthalmologist for patients with very dense cataracts to assess the retina function.

by Dr. Craig Miller | Eye Columbus