Recruit NTG patients, who are not treated with the glaucoma medication recent 2 months. If treated, after washout period of 4 weeks, the patients can be included in the study. Baseline IOP, systolic and diastolic BP will be measured. (Day 1) After 4 weeks of treatment of Cosopt or Xalatan, all participants will be checked diurnal IOP, systolic and diastolic BP. IOP was measured by Goldmann applanation tonometry (mean of three consecutive readings) with the patient in a sitting position at the slit lamp. Every IOP will be measured by one masked glaucoma specialist who is unaware of the treatment assignments. After the IOP measurements, after a 5-minite rest, pulse rate and BP (systolic and diastolic) of radial artery were measured in the sitting position using a standard automated blood pressure cuff. During the period, all measuring instruments keep to be calibrated by the manufacturer's instruction.