Patients with open angle glaucoma and a history of relative stability of the visual field are followed for 18 months. A visual field is measured every 3 months for a total number of n = 6 eligible fields at the end of this phase. Then, those eyes showing progression of the field (i.e. deterioration of th eexisting glaucoma), are randomized to receive either 0.2% brimonidine tartrate eyedrops b.i.d. or 360° argon laser trabeculoplasty in one session. Either treatment will be put "on top" of the pre-existing anti-glaucoma therapy. Then, a further 18-month phase is planned, with a sequnece of field taken at the same pace as the previous phase. Progression is detected (and measured) acording to a trend-analysis (i.e. regression vs time of single points and of clusters of adjacent points).
