Describe the protein content and solubility changes in the lens with age.

• A. High protein content with more soluble when young and more insoluble when older
• B. Low protein content with solubility increasing with age
• C. High protein content with constant solubility
• D. Low protein content and always insoluble

Answer: (A)

Lens crystallin proteins make up a high protein content that's essential for clarity. In youth, these proteins are largely soluble, allowing light to pass through with minimal scattering. As the eye ages, the crystallins undergo chemical changes—oxidation, cross-linking, and other modifications—that reduce their solubility and promote aggregation. This shift from soluble to insoluble protein leads to light scattering and opacity, i.e., cataract formation. So the description that fits best is high overall protein content with proteins being more soluble when young and becoming more insoluble with age. The other options don’t fit because they imply low protein content, increasing solubility with age, constant solubility, or perpetual insolubility, none of which align with how lens proteins behave over time.