A retrospective 12-year study on 35 patients having IOP values higher than 21 mmHg in repeated tonometric curves with no clinical glaucomatous-type signs was carried out with the aim of discovering the incidence of the eyes which evolved towards the glaucomatous disease, to evaluate the role of the preventive therapy and to observe how response to the ibopamine provocation test (which assesses outflow pathway compromission) was modified with time. The data obtained showed that, in 39.13% of the eyes, there was an evolution towards the disease. The ibopamine test was positive at time "0" (study begins) in 48.14% in the evolutive eyes and in 66.66% of the eyes which remained stable, while, at time "12" (study ends), almost all of the eyes (92-95%) had become positive. The role of precociously initiated ocular hypotensive therapy concurring with the test positivity is put in evidence.