What is the cup-to-disc ratio? What is it useful for glaucoma diagnosis? The cup-to-disc ratio is the ratio of the dip diameter of the optic disc cup to the dip diameter of the optic disc (C/D), as shown in the figure. It has been emphasized that the cup-to-disc ratio is of greater value in the diagnosis of glaucomatous optic nerve damage, but currently the disc rim pattern is used to describe glaucomatous optic nerve morphologic damage, and the cup-to-disc ratio is only an indicator. Of course, the narrowing of the disc rim (the presence of optic nerve damage) is accompanied by an enlargement of the cup-to-disc ratio. How is the cup-to-disc ratio measured? Does the interpretation of different doctors have an effect on the results? In clinical practice, it is usually a visual measurement by the doctor. There is a difference in the interpretation of different doctors. What is the normal value of the cup-to-disc ratio? What kind of test results indicate a problem? The cup-to-disc ratio is traditionally considered to be <0.6, but in fact, a large optic disc with a larger cup, sometimes up to 0.8, is not abnormal. It is only when the cup-to-disc ratio is enlarged and there is a combination of changes in the retinal nerve fiber layer that glaucoma changes. How can I tell if the cup is physiologically large or if it is caused by glaucoma? Physiological macroglossia is a condition in which the disc is large but the disc rim pattern and retinal nerve fiber layer are normal. Physiological macropia is static and unchanged at the time of follow-up. Will the cup-to-disc ratio continue to increase as the disease progresses? If the cup-to-disc ratio becomes larger, does that indicate possible glaucoma? Do I need treatment? If glaucoma is allowed to progress naturally without intervention, the cup-to-disc ratio will continue to increase as the disease progresses until you become completely blind. A larger cup-to-disc ratio at follow-up, along with changes in the retinal nerve fiber layer, is an indication of glaucoma. Treatment is certainly needed. Is the cup-to-disc ratio of a child the same as that of an adult? Will the problem be treated the same way when it is detected? The cup-to-disc ratio of a normal child is no different from that of an adult. In young children with glaucoma, without intervention, the cups expand more rapidly and tend to expand in concentric circles. Management varies depending on the type of glaucoma. The surgical approach to glaucoma in young children is different from that of adults.