Which part of the eye is primarily affected in glaucoma?

In glaucoma, the primary structure affected is the optic nerve. Glaucoma is a group of eye conditions that can lead to damage of the optic nerve, which is essential for transmitting visual information from the eye to the brain. This damage is often associated with increased intraocular pressure, which can compress the optic nerve fibers and ultimately lead to vision loss if not managed properly.

While the retina plays a crucial role in capturing light and initiating the process of vision, in glaucoma, it's the optic nerve that suffers the direct consequences of elevated pressure and is pivotal in how the disease manifests. Other structures such as the lens and cornea are involved in focusing light and protecting the eye, respectively, but they are not directly impaired by glaucoma itself. Thus, the optic nerve's health is central to the understanding of glaucoma and its impact on vision.