Compounds are disclosed of the general formula I ##STR1## wherein R.sub.1 is a group of the formula IIR.sub.3 --X-- IIwherein R.sub.3 is alkyl; phenyl; phenyl substituted with halogen, lower alkyl, hydroxy, lower alkoxy, or phenoxy; phenyl-lower alkyl in which the phenyl group may be substituted with halogen, lower alkyl, hydroxy, lower alkoxy, or phenoxy; phenyl-lower alkenyl in which the phenyl group may be substituted with halogen, lower alkyl, hydroxy, lower alkoxy or phenoxy; and X is oxygen or sulfur; or R.sub.1 is a group of the formula III ##STR2## wherein R.sub.4 has the same meaning as R.sub.3 as defined above; or R.sub.4 is a group of the formula IV ##STR3## wherein R.sub.7 has the same meaning as R.sub.3 as defined above; or R.sub.7 is an aromatic 5- or 6-membered heterocyclic ring containing one or two heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur; and wherein R.sub.5 and R.sub.6 are the same or different and each represent hydrogen or have the same meaning as R.sub.3 as defined above;or R.sub.1 is a group of the formula V ##STR4## wherein R.sub.5 and R.sub.6 are as defined above and R.sub.8 is polyhalogenated lower alkyl or a group of the formula VI ##STR5## wherein R.sub.3 is as defined above; or R.sub.1 is a group of the formula VII ##STR6## wherein R.sub.10 and R.sub.11 together with the adjacent nitrogen atom form a 5- or 6-membered heterocyclic ring, which in addition to the nitrogen may contain one or two further heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur;or R.sub.1 is a group of the formula VIII ##STR7## wherein R.sub.13 is a group of the formula II, wherein R.sub.3 and X are as defined above; or R.sub.13 is a group of the formula VIIa ##STR8## wherein R.sub.16 and R.sub.17 are the same or different and each represent hydrogen or have the same meaning as R.sub.3 as defined above; or R.sub.13 is a group of the formula VII, wherein R.sub.10 and R.sub.11 are as defined above;or R.sub.1 is a group of the formula IX ##STR9## wherein R.sub.13 is as defined above; and R.sub.2 is hydrogen or a group of the formula IV, wherein R.sub.7 is as defined above; or R.sub.2 is a group of the formula VI, wherein R.sub.3 is as defined above; and salts thereof.The compounds of the formula I are prodrugs of pilocarpine. When administered ophthalmically to a warm-blooded animal, such as a human, compounds of formula I, due to their high lipophilicity, will penetrate the cornea in an extent greater than pilocarpine itself, and will thereafter be converted into pilocarpine in a slow and controlled manner.