Caffeine Consumption in Glaucoma Patients and Healthy Subjects

Inclusion Criteria: * age 18 to 90 years * diagnosis of primary open angle glaucoma (Mild, Moderate and Advanced) * healthy subjects with no eye disease Exclusion Criteria: * Diseases, ophthalmic or systemic, that are likely to affect OCTA results * greater than moderate cataract * nystagmus * inability to look at target * macular degeneration other than mild drusen or pigmentary changes * diabetic retinopathy * neovascular glaucoma or non-glaucoma optic neuropathies * current macular edema, prior laser to retina, inflammatory retinopathy or choroidopathy * keratoconus, corneal ectasia, central corneal scarring * rheumatologic diseases or Raynaud's phenomena * pregnant and lactating women * mental illness or alcohol addiction * pre-existing bladder symptoms, cardiac disease or sleep disorder * refractive spherical diopter greater than 5 or cylinder greater than 3 * possible tolerance to caffeine (drinking more than 1 cup coffee per day).