the invention relates to the use of cyclopentane heptanoic acid , 2 - thiocarbamoyloxy and carbamoyloxy as therapeutic agents e . g . as ocular hypotensives . the compounds used in accordance with the invention are represented by the following formula i : wherein a wavy segments indicate either the alpha or beta configuration ; the dashed bond represents a double bond or a single bond ; ar is selected from the group consisting of aryl or heteroaryl radicals having from 4 to 10 carbon atoms and substituted derivatives of said aryl and heteroaryl radicals ; n is 0 or an integer of from 1 to 4 ; x and y are 1 or 0 , provided that when x is 1 , y is 0 and when x is 0 , y is 1 ; r 1 is hydrogen or a lower alkyl radical or a substituted lower alkyl radical having up to six carbon atoms ; x is selected from the group consisting of — or 1 and — n2 ; y is ═ o or represents 2 hydrogen radicals , and the 9 and / or 11 esters thereof and / or the pharmaceutically acceptable salts of said compounds and / or esters .