A number of 17-aryl trinor and 16-aryloxy tetranor PGF2α derivatives have been approved for the treatment of glaucoma. These “ring” prostaglandin analogs have improved efficacy over the prostaglandins with an n-alkyl lower side chain. Of these, the ones wherein the 13,14-double bond has been hydrogenated retain relatively good potency, but show a significantly reduced incidence of local irritant side effects. 17-TFM-PGF1α is a typical “ring” analog reminiscent of the trifluoromethyl-phenoxy ring of Travoprost. The a chain of 17-TFM-PGF1α is saturated, making this compound a formal member of the one-series PGs. Recent work has shown that in the “ring” series of analogs, this modification has little impact on FP receptor binding. As an ocular hypotensive agent, it is expected that 17-TFM-PGF1α would act very much like the free acid of latanoprost.