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.
UPDATE: Now I hear Denzel Washington is considering directing a film version of Fences. (Bravo!) The last time he helmed a pic was The Great Debaters in 2007 and, of course, Antwone Fisher in 2002. The toughest thing when great movie stars head to Broadway is that their performances live in the moment.