What lead thickness equivalence is required for protective glasses?

• A. 0.25 mm Pb
• B. 0.35 mm Pb
• C. 0.5 mm Pb
• D. 1.0 mm Pb

Answer: (B)

Protective eyewear is rated by lead equivalence, which is the thickness of lead that would give the same attenuation as the glasses. For diagnostic radiology, the commonly specified minimum is 0.35 mm lead equivalent. This thickness provides sufficient attenuation of scatter radiation to protect the eye lens while keeping the glasses reasonably light and comfortable. A thinner value, like 0.25 mm, would offer less protection against scatter, whereas thicker values such as 0.5 mm or 1.0 mm add more attenuation but are heavier and not generally required for routine diagnostic energies. If the beam energy were much higher, other protection considerations might come into play, but for standard clinical practice, 0.35 mm Pb is the typical requirement.