Introduction Several studies have shown intra-ocular pressure (IOP) reductions following lifestyle and behavior changes in primary open-angled glaucoma (POAG) in the short term. Our aim in this study was to examine the potential of such interventions as an adjunct treatment and assess their cumulative short-term effect on IOP and illness perception in patients with POAG. Methods In this randomized, parallel-arm, single blind controlled trial, POAG patients were randomized in a 1:1 ratio to either a treatment group which received instructions on dietary and lifestyle changes in addition to their standard therapy or to a control group which continued their standard therapy. Recommendations were selected to include those previously reported to reduce IOP; including: Saffron spice supplementation, high fiber diet, avoidance of caffeine, aerobic exercise, head elevation during sleep and others. Illness perception was assessed using the Brief IPQ questionnaire. Results 22 participants were enrolled, 3 were lost to follow-up and 19 entered analysis. Mean age was 69 ± 12 and 12 (63%) were female. Concerns about the illness, symptoms, and feelings of control were significantly improved in the treatment group compared with controls (all P Conclusions Dietary and lifestyle changes may improve illness perception and patient well-being, however they do not appear to affect IOP in the short term among patients with POAG.