Glaucoma is a progressive optic neuropathy and early detection is key to preventing vision loss from the disease. Many patients can show progressive structural changes despite the absence of detectable losses on visual field. These structural changes are usually quantified by imaging technologies, such as optical coherence tomography (OCT). This technology can provide quantitative and reproducible measurements of the peripapillary retinal nerve fiber layer, optic nerve head, and macula, which have been shown to be helpful in the early detection of disease progression. Therefore, clinicians should be aware on how to properly use the progression tools provided by OCT.