The present invention provides a method of treating ocular hypertension or glaucoma which comprises administering to an animal having ocular hypertension or glaucoma therapeutically effective amount of a compound represented by the general formula I;wherein a hatched line represents the alpha configuration, a triangle represents the beta configuration, a straight line, e.g. at the 9, 11 or 15 position represents either the alpha or beta configuration, a dotted line represents the presence or absence of a double bond; a wavy line represents a cis or trans bond;X is O, S, NH or (CH2)n;n is 0 or an integer of from 1 to 4;Y is C1-C5 n-alkyl, C3-C7 cycloalkyl, phenyl, furanyl, thienyl, pyridinyl, thiazolyl, benzothienyl, benzofaranyl, naphthyl, or substituted derivatives thereof, wherein the substituents maybe selected from the group consisting of C1-C5 alkyl, halogen, CF3, CN, NO2, N(R2)2, CO2R2 and OR2;Z is (CH2)n or a covalent bond;R is C1-C6 lower alkyl or Z-CF3 or mesylate or triflate;R1 is H, R2 or COR2;andR2 is H or C1-C5 lower alkyl or 9, 11 or 15 esters thereof.