Final answer:
A Christmas tree cataract is a rare eye condition characterized by the appearance of small, crystal-like opacities in the lens of the eye. They are caused by a genetic mutation and resemble the shape of a Christmas tree when observed under a microscope.
Step-by-step explanation:
A Christmas tree cataract is a rare eye condition characterized by the appearance of small, crystal-like opacities in the lens of the eye. These opacities resemble the shape of a Christmas tree when observed under a slit-lamp microscope, hence the name. They are caused by a genetic mutation that affects the growth and development of lens fibers, resulting in the formation of abnormal crystalline structures.