Final answer:
Cataracts are a clouding of the lens in the eye that can lead to vision loss. The cause of 'Christmas tree cataract' is not specified in the question.
Step-by-step explanation:
Cataracts are a clouding of the lens in the eye that can lead to vision loss. It is not clear from the provided information what 'Christmas tree cataract' refers to specifically. However, it is important to note that cataracts can be caused by various factors including age, UV exposure, and certain medical conditions.