Gripe of the morning: All eyeglass websites do faceting and search wrong.
Frame designs are fully segregated by "men" and "women". A minority have a "unisex" section. Sometimes it is an intersection of the gendered sets, sometimes it is an exclusive third set.
The only parameter I care to filter on is lens size. Very few accommodate that, and those that do require me to redo for each gender-section.
Eyeglass gender should be a category facet that can be toggled just like any other category.