Waveform Analysis of the Doppler Curve of Ophthalmic Arteries in Glaucoma Patients

Color Doppler Imaging (CDI) has been providing information about ocular blood flow over the past decades. This non-invasive procedure based on ultrasound technique has identified increased resistance and decreased systolic blood velocities to exist in the ophthalmic arteries of glaucoma patients. However, existing data has provided very little information regarding the analysis of the Doppler waveform in itself and to whether variables such as early systolic acceleration or systolic/diastolic velocity ratios are of any significance in glaucoma disease. In other medical specialties using CDI technology, such as nephrology or cardiology for instance, this analysis has been part of the normal routine. This information has been used in screening patients for disturbed circulation such as arterial stenosis or providing information regarding prognosis of renal and hepatic transplants have been used for decades now. What is the normal characteristics of the waveform Doppler analysis? To answer this, the investigators will create a normative database using healthy controls. Are there signs of altered stiffness or compliance in the ophthalmic arteries of glaucoma patients? To answer this, the analysis of early acceleration acceleration and detection of an early peak systolic will be done on the Doppler curves of glaucoma patients and compared to the healthy normative database. Are there any difference between the two types of glaucoma \[primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG)\]? The investigators will compare the variables of the ophthalmic artery waveform in these two groups. Do any of these Doppler waveform variables have any clinical significance? To answer this, the investigators will search for the existence of any correlation between the waveform data and both functional (visual field testing) and structural (Confocal scanning laser ophthalmoscopy - CSLO) variables of the glaucoma groups.