intraocular pressure in warm - blooded animals is reduced by topically applying to the eye thereof , an effective ophthalmologically acceptable amount of a compound of the formula : ## str1 ## wherein r represents a member selected from the group consisting of hydrogen or a c 1 - c 5 straight or branched alkyl group ; and wherein r 1 and r 2 , which may be the same or different , represents an acyl member selected from the group consisting of alkanoyl having 1 - 22 carbon atoms , alkenoyl having one or two double bonds and having 4 - 22 carbon atoms , ## str2 ## having a total of 4 - 10 carbon atoms of which 3 - 7 are ring carbon atoms in cycloalkyl and wherein n is zero , one , or two , phenoxyacetyl , naphthalenecarbonyl , pyridinecarbonyl , ## str3 ## wherein n is zero , one or two and phenyl is unsubstituted or is substituted by 1 - 3 alkyl having 1 - 4 carbon atoms , alkoxy having 1 - 4 carbon atoms , halo , trifluoromethyl , dialkylamino having 2 - 8 carbon atoms , and alkanoylamino having 1 - 6 carbon atoms ; or an ophthalmologically acceptable acid addition salt thereof .