Chart review will be performed to select potential glaucoma participants. These potential participants will be invited to participate in the study, either by phone or face-to-face during scheduled visits.

Control participants will be invited from a registry that contains names of prior research participants who have agreed to be contacted about future studies (participants have worn ambulatory blood pressure monitor or ABPM in the past).

Invited persons who agree to participate in the study will be scheduled for a screening visit at the eye clinic, during which they will learn more about the study. On the day of the screening visit, they will be provided with detailed information about the study, after which they will decide whether or not to participate. If they agree, they will sign the consent form. The screening visit will then be conducted by the research personnel and will take place at the eye clinic in a designated closed office and will include measurement of visual acuity, assessment of the anterior and posterior segments of the eye, measurement of IOP by Goldmann applanation tonometry. If after the screening exam it is determined that they do not qualify for the study, they will be told why they are being excluded. Healthy controls as well as glaucomatous patients not on treatment will be fitted with the BP and IOP monitoring devices. Those who are on glaucoma medication will be asked to stop their medication starting the day following the screening visit for the duration detailed in the inclusion criteria, and be given an appointment for the for IOP and BP measurement. On the appointment day, they will be fitted the BP and IOP monitoring devices. The BP monitor will be set up to take the measurements automatically every 30 min during the day and every hour at night until the next morning. The IOP monitor will take measurements every 10 minutes during the 24-hour period. Both devices are computerized and record all the measurements and reading times. Patients will be required to return to the clinic the next morning for removal of the devices, after which there will be no further visits.

1. This study will provide for the first time information on the safety, tolerance, and acceptability of the two devices used together. It will also provide preliminary information on the reasons why people may drop out of the study, and information about the relationship between IOP, BP, and OPP in patients with normal tension glaucoma and in healthy controls.
2. IOP will be measured with the Sensimed Triggerfish, which is a disposable silicone contact lens embedded with a wireless sensor. The sensing resistive gauge in the device is circular around the center of the lens and is placed over a circumference of 11.5 mm in diameter. This corresponds to the corneoscleral junction position, where maximum corneal deformation occurs as a result of changes in IOP. A soft patch containing the receiving antenna will be applied around the eye and transmits the information via wire to the recorder that the patient will wear around the waist. The patient can continue to wear spectacles during monitoring. The device records a total of 144 measurements over a 24-hour period. Measurements are taken every 10 min for a total duration of 1 min. The results obtained are presented in an arbitrary unit and not mm Hg. In this study, tonometry will be performed using radiofrequency waves at 27 MHz from the external antenna, which is embedded in the patch applied around the patient's eye.