If you would like to combine these searches, you can. Simply add "and" between two words to search for frames that are both metal and men's, for example.
Also, you can follow these simple instructions
to better implement your search:

men's plastic

finds documents containing 'men's' or 'plastic'

men's or plastic

same as above

men's and plastic

finds documents containing both 'men's' and 'plastic'

men's not plastic

finds documents containing 'men's' but not 'plastic'

(men's not plastic) and eyewear

finds documents containing 'eyewear', plus 'men's' but not 'plastic'

unisex*

finds documents containing words starting with 'unisex'