Influence of forehead gap size on eye protection provided by lead eyewear worn over prescription glasses: A Monte Carlo study

Background Due to exposure to high levels of scattered ionizing radiation, interventional radiology (IR) physicians have an elevated risk of radiation‐induced eye injuries and cataracts. Previous studies have evaluated the protective effects of regular lead glasses and recommended measures to improve radiation protection for the eyes. However, the protective effects of fit‐over eyewear—lead eyewear worn over prescription glasses—have not been thoroughly examined. Importantly, a previous study noted that the space required to accommodate prescription glasses may reduce eye protection. Purpose Monte Carlo (MC) simulations were performed to quantify the protective effects of fit‐over eyewear and assess the relative effectiveness of adding bottom shields to conventional lead eyewear to improve eye protection. Methods Conventional lead glasses comprising front and side lenses and prescription glasses with plastic lenses and titanium frames were modeled. Lead glasses with bottom shields were created by bending the lower edges of the front lenses of conventional eyewear without increasing the total lens area. Three lead lens thickness values were tested: 0.07, 0.5, and 0.75 mm. Using a mesh‐type reference computational phantom representing an adult male to simulate an IR physician, MC simulations were performed with a transcatheter arterial chemoembolization setup. The Particle and Heavy Ion Transport code system was used to calculate the radiation dose deposited in each eye‐sensitive volume. The distance ( d ) between the forehead and front lead lens varied systematically. Protective effects were evaluated using the shielding rate (%) calculated as: (1‐ D pr / D 0 ) × 100, where D 0 is the radiation dose without protection and D pr is the dose with eye protection. Results For the eye near the X‐ray source (left eye), the conventional models showed shielding rates >50% when the lead thickness was 0.5 or 0.75 mm and d was ≤0.5 cm. The conventional 0.07‐mm lead eyewear exhibited shielding rates <50% when d was 0.5 cm, and <26% when d was ≥0.8 cm. However, 0.07‐mm lead eyewear with bottom shields maintained approximately 50% shielding when d increased to 1.0 cm. The models using 0.5‐ or 0.75‐mm lead lenses with bottom shields exhibited shielding rates >76% at d = 1.0 cm. Notably, the shielding rates for the right eye were <12% regardless of introducing bottom shields. The right eye doses were 45–48% of the left eye lens dose without protection. Conclusion By quantifying the relationship between the size of the lens gap and shielding rates, this study estimates the protective effects of fit‐over eyewear and can help IR physicians select suitable eyewear. Our findings show that fit‐over eyewear with bottom shields effectively protects the left eye during posterior‐anterior projection. Although introducing bottom shields can improve conventional side‐shield models in terms of increased shielding rate for the left eye, the shielding rates for the right eye remained low because of the gap around the nose. Further study of new designs with a shielded covering over the nose may be warranted.