A system comprising an external electronic device and a combination device (100, 200, 300, 400, 500, 600, 700, 1200) for tonometric measurement and drug application on an eye, the combination device (100, 200, 300, 400, 500, 600, 700, 1200) comprising: a device enclosure housing a tonometric measuring unit (101, 201, 301, 401, 501) for acquiring an intraocular pressure measurement of the eye and a drug administration unit (113, 213, 222, 313, 322, 413, 422, 522) for applying a drug to the eye; a drug reservoir (105, 205, 305, 405, 505, 605, 705, 805, 1205) attachable to the device enclosure, wherein the drug administration unit (113, 213, 222, 313, 322, 413, 422, 522) controls the withdrawal of one or more drugs from the drug reservoir (105, 205, 305, 405, 505, 605, 705, 805, 1205) for application to the eye; a dosage monitoring unit that obtains a measure of the amount of drug applied to the eye; and a communication unit (121, 221, 321, 521) for establishing a communication link to the external electronic device, and for exchanging information between the combination device (100, 200, 300, 400, 500, 600, 700, 1200) and the external electronic device, characterized in that the system comprises an electronic data processor (Cpnt1) that determines an effectiveness-measure of applied individual drugs based on their applied dosage and consequent effect on monitored IOP measurement as compared with previous dosage applications, and issues an alert in response to an individual drug having a determined effectiveness-measure less than a first predefined threshold or greater than a second predefined threshold higher than the first predefined threshold; wherein the external electronic device includes the electronic data processor (Cpnt1). a device enclosure housing a tonometric measuring unit (101, 201, 301, 401, 501) for acquiring an intraocular pressure measurement of the eye and a drug administration unit (113, 213, 222, 313, 322, 413, 422, 522) for applying a drug to the eye; a drug reservoir (105, 205, 305, 405, 505, 605, 705, 805, 1205) attachable to the device enclosure, wherein the drug administration unit (113, 213, 222, 313, 322, 413, 422, 522) controls the withdrawal of one or more drugs from the drug reservoir (105, 205, 305, 405, 505, 605, 705, 805, 1205) for application to the eye; a dosage monitoring unit that obtains a measure of the amount of drug applied to the eye; and a communication unit (121, 221, 321, 521) for establishing a communication link to the external electronic device, and for exchanging information between the combination device (100, 200, 300, 400, 500, 600, 700, 1200) and the external electronic device, characterized in that the system comprises an electronic data processor (Cpnt1) that determines an effectiveness-measure of applied individual drugs based on their applied dosage and consequent effect on monitored IOP measurement as compared with previous dosage applications, and issues an alert in response to an individual drug having a determined effectiveness-measure less than a first predefined threshold or greater than a second predefined threshold higher than the first predefined threshold; wherein the external electronic device includes the electronic data processor (Cpnt1).