Christmas tree cataract

From an interesting case report posted by Drs. Obi and Weir in the BMJ 2010;341:c6644:

A 73 year old woman referred for cataract surgery had on examination a left Christmas tree cataract (fig 1A). Highly reflective, iridescent, polychromatic crystals were noted within the lens. Their colours varied according to the angle of the incident light, (fig 1B, C). We postulate that Christmas tree cataracts result from the accelerated breakdown of membrane associated proteins. The peptides and amino acids accumulate in the lumen of the reticular meshwork, and cystine is concentrated beyond the level of crystallisation, giving rise to growing crystals.