The type of dose response curve associated with cataract formation is:

• A. Linear non-threshold
• B. Linear threshold
• C. Non-linear non-threshold
• D. Non-linear threshold

Answer: (D)

Cataract formation from radiation is a deterministic effect, where there is a dose level below which no cataracts occur and above which risk and severity increase, but not in a straight-line fashion. The lens does not show opacity until a certain threshold dose is reached, and once that threshold is passed, the relationship between dose and effect rises in a curved (non-linear) way rather than a simple straight line. So the best description is a non-linear threshold curve: a no-effect region below the threshold, followed by a non-linear increase in risk as dose increases. This differs from a linear non-threshold pattern (risk at any dose) or a linear increase after threshold, which don’t fit the lens’s dose-response behavior.