“TREE BRANCH ILLUSION” COMMONLY SEEN DURING EYE EXAMS

“Wow, I can see a reflection of my own blood vessels!” – this is a frequently heard comment in our exam rooms from patients who are undergoing an eye exam. It can happen when we are shining a bright light into the eyes, at that point often a shadow is briefly seen resembling tree branches. This is known as a “Purkinje Tree”.

The retina is the inner surface of the back of the eye, and it contains blood vessels like most living tissue. Under most types of light we would not see these blood vessels, however during situations where a very bright light is shone into the eye at an angle, a brief shadow of the branching vessels is produced. Our eyes quickly adapt to the new image and the shadow soon disappears.

Purkinje Trees are one of several types of entoptic phenomena, visual illusions that result from processes that occur within our eyes – some normal and some abnormal. They were first described in the early 1800’s, and there are several different kinds. A few are described below:

• Moore’s lightning streaks. These are flashes of light that many of our patients have seen arise suddenly off to the side in one eye. They are caused by changes to the gel within the eye – if seen they may pose a risk of retinal detachment and should be evaluated by your MVO optometrist within one to two days.
• Blue arc. In a dark room, looking adjacent to a small brightly lit object (such as a digital clock) will often produce briefly seen arches of blue light. This is normal, and may be the result of the arrangement of the cells around the central part of the retina and how they conduct an electrical signal when exposed to light.
• Flying corpuscles. These are often seen when looking into a bright background without much visual detail (such as outside of an airplane window) and look like tiny circles moving quickly, one after the other. These are thought to be single blood cells moving through a capillary (microscopic blood vessel) very close to the most central and most sensitive part of your vision. They are completely normal.

Any change in your vision should be evaluated by your MVO optometrist. We will be able to diagnose your condition and determine whether what you’re seeing requires further treatment or management.

• Dr. Tom Wilk