What lead thickness equivalence is required for protective glasses?

• A. 0.15 mm lead (Pb)
• B. 0.25 mm lead (Pb)
• C. 0.35 mm lead (Pb)
• D. 0.50 mm lead (Pb)

Answer: (C)

Protective eyewear is chosen by its lead equivalent to reduce the lens dose from scattered X-rays during diagnostic procedures. The lens of the eye is particularly radiosensitive, so shielding aims to lower long-term risk. Lead thickness determines how much X-ray energy is attenuated: more thickness means more attenuation, but heavier, more cumbersome glasses.

For typical diagnostic energies, a lead-equivalent of about 0.35 mm provides enough attenuation to protect the lens from scatter without making the glasses too heavy for regular use. Thinner options would let more scatter through, offering less protection, while thicker options would add weight with only marginal additional benefit in many clinical situations. Therefore, 0.35 mm lead equivalent is the practical and effective standard for protective glasses.