Christmas Tree Cataract

A cataract that contains highly refractile multicoloured 'needles' crisscrossing the lens fibres of the deep cortex. The needles’ colours vary according to the angle of incident light, and in retroillumination reveal only a dim outline of the cataract, suggesting that the Christmas tree cataract is a diffractive phenomenon. Analysis of the cataracts by scanning EM, energy-dispersive x-ray and Raman microanalysis leads to the conclusion that the needles are probably composed of cystine and the resulting age-related aberrant breakdown of crystals is induced by elevated Ca2+ levels
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