This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lens, Subject name: Ophthalmology
Cataract brunescen results due to deposition of- 
Select and explain. 
A. Urochrome, B. Copper, C. Iron, D. Silver
A: Urochrome
Answer: A: Urochrome 
Explanation: "Nuclear sclerosis also distos color vision because of-yellow-brown urochrome pigment, chich accumulates in the lens and filters blue wavelenths of light". Older nuclear cells lose organelles and cell membranes, with increasing density and dehydration dnd accumulation of yellow urochrome pigment (possible photo-oxidation product). When advanced, it becomes brown (brunescent) or black (cataracta nigra). Ref: Eye pathology : An Atlas and text p.110.