... main types are: Open-angle glaucoma , also called primary open-angle glaucoma. This is the most common type. It's called "open" because the canals that lead to your eye's drainage system are open. But deeper inside the drainage system, clogs develop. These clogs slow the fluid drainage. Open-angle glaucoma tends to affect both eyes. In the early stages, Most people don't have any symptoms or vision changes. But without treatment, peripheral (side) vision is usually lost first. Closed-angle glaucoma , also called angle-closure or narrow-angle glaucoma. In this uncommon type ...