When the retina is separated from this layer of the eye, it is said to be detached. In most cases, this detachment is the result of a tear or hole in the retinal tissue. Fluid passes through the opening in the retina and separates the retina from the underlying choroid. Open-angle glaucoma, the most common form of glaucoma, affects about 3 million Americans–half of whom don't know they have it. It has no symptoms at first, but over years it can steal your sight. With early treatment, you can often protect your eyes against serious vision loss and blindness.