The refractive index of current eyeglass lens materials ranges from 1.498 (CR-39 plastic) to 1.74 (a specific variety of high-index plastic). So for the same prescription power and lens design, a lens made of CR-39 plastic will be the thickest lens available, and a 1.74 high-index plastic lens will be the thinnest.
Principal photography on the film began on April 25, 2016, in Pittsburgh, Pennsylvania, in the Hill District, and wrapped in mid-June 2016. Fences was released in the United States on December 16, 2016, by Paramount Pictures, received positive reviews and grossed $64 million.
Recognizing the effectiveness of physical barriers as a means of border control, Congress first mandated the construction of a border fence in 1996 as part of the Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA). By 2004, only nine miles of fencing were completed. Congress subsequently passed the Secure Fence Act of 2006.