Purpose: to study the role of IOP on the progress of treated primary open angle glaucoma patients. Material: 447 eyes of 256 treated POAG patients in glaucoma department from 2004- 2008, divided into 3 group: Group I: high risk of losing visual function, group II: moderate risk of losing visual function, group III: glaucoma suspect with moderate risk of losing visual function. Methods: describe, cross design, no control. Results: eyes whose IOP from 17-21 mmHg are major (61.1 percent), whose IOP 17mmHg are 20.6 percent, there are still 18.3 percent eyes having IOP 21mmHg. The rate of progress when IOP 17mmHg is 2.1 percent, meanwhile this rate when IOP 21mmHg is 35.3 percent (p 0.01). The rate of reached target IOP in group I is 62.8 percent, in group II is 71 percent, in group III is 67.9 percent. The rate of progress of reached target IOP eyes in group I is 20.7 percent, group II is 22.5 percent, in group III is 15.7 percent, lower than unreached target IOP (group 1- 32.6 percent, group 11- 38. 7 percent, group III - 20.5 percent) (P 0.05). The progress of the disease when the IOP fluctuation 1 mmHg is only 2. 7 percent, when the IOP fluctuation from 1-2mmHg is 13.7 percent, and it reaches 83.7 percent when IOP fluctuation 6mmHg. Conclusion: the relatively safe IOP for the progress of the disease is 17mmHg (Tonometry Maclakov). The target IOP should be based on the severity of the disease. IOP fluctuation has an important role on the progression of the disease.