Retinal Blood Flow and Autoregulation

This study is measuring blood flow in the retina and examining the eye's ability to automatically regulate that blood flow in people with early glaucoma, pre-glaucoma (glaucomatous optic nerve damage without vision loss yet), or healthy eyes, to better understand how blood flow changes relate to vision loss. **You may be eligible if...** - You are 18 years or older - You have an open-angle structure in your eye (grade 3 or 4) - Your prescription is between -8.00 and +3.00 diopters - Your best-corrected vision is 20/25 or better - You fall into one of these categories: early glaucoma, pre-perimetric glaucoma (nerve damage without visual field loss), or healthy eyes **You may NOT be eligible if...** - You are on glaucoma medications and unwilling to pause them for 4 weeks - You have other significant eye conditions - You do not meet the vision or prescription criteria Talk to your doctor to see if this trial is right for you.